BAB AL-SALAM, Syria Syrian forces bombarded parts of Damascus with helicopter gunships on Sunday, witnesses said, driving rebels out of a northern district a week after opposition fighters launched a major assault on the capital.
Members of a Syrian army division under the command of President Bashar al-Assad's brother summarily executed several young men, a witness and opposition activists said.
In a further escalation of a conflict that opponents of Assad have turned into all-out civil war, fighting raged around the intelligence headquarters in the biggest city Aleppo and in Deir al-Zor in the east.
Syrian forces regained control of one of two border crossings seized by rebels on the frontier with Iraq, Iraqi officials said, but rebels said they had captured a third border crossing with Turkey, Bab al-Salam north of Aleppo.
"Seizing the border crossings does not have strategic importance but it has a psychological impact because it demoralizes Assad's force," a senior Syrian army defector in Turkey, Staff Brigadier Faiz Amr, told Reuters by phone.
"It's a show of progress for the revolutionaries, despite the superior firepower of Assad's troops."
The rebels said they lost 12 men and 40 were wounded during a 24-day siege they mounted to take the Bab al-Salam border post. The rebel commanding officer in the area, Abu Omar, said they took the crossing point on Sunday without a fight.
"There were two armored vehicles at the gate and they escaped. This is a safe zone for us and we don't expect the army to come and attack," said Omar. "Eighty percent of the area here is in rebel hands anyway," he added.
The bombardments in Damascus and Deir al-Zor were some of the fiercest yet and showed Assad's determination to avenge a bomb on Wednesday that killed four members of his high command.
It was the gravest blow in a 16-month-old uprising that has turned into an armed revolt against four decades of Assad rule.
Rebels were driven from Mezzeh, the diplomatic district of Damascus, residents and opposition activists said, and more than 1,000 government troops and allied militiamen poured into the area, backed by armored vehicles, tanks and bulldozers.
Three people were killed and 50 others, mostly civilians, were wounded in the early morning bombardment, said Thabet, a Mezzeh resident. "The district is besieged and the wounded are without medical care," he said.
"I saw men stripped to their underwear. Three buses took detainees from al-Farouk, including women and whole families. Several houses have been set on fire."
The neighborhood of Barzeh, one of three northern areas hit by helicopter fire, was overrun by troops from the Fourth Division, commanded by Assad's younger brother, Maher al-Assad, 41, who is widely seen as the muscle maintaining the Assad family's Alawite minority rule.
"At least 20 Fourth Division tanks and hundreds of its members entered Barzeh this afternoon," opposition activist Abu Kais said by phone from the district.
"I saw troops go into the home of 26-year-old Issa al-Arab. They left him dead with two bullets in his head. Seventeen-year-old Issa Wahbeh was pulled from a shelter and beaten and killed. Four other males in their 20s were killed this way,"
His role has become more crucial since Assad's defense and intelligence ministers, a top general and his powerful brother-in-law were killed by the bomb on Wednesday, part of a "Damascus volcano" by rebels seeking to turn the tables in a revolt inspired by Arab Spring uprisings in Tunisia, Libya and Egypt.
Assad has not spoken in public since the bombing. Diplomats and opposition sources said government forces were focusing on strategic centers, with one Western diplomat comparing Assad to a doctor "abandoning the patient's limbs to save the organs".
Assad is still in Damascus and retains the loyalty of his armed forces, the Israeli military said, after questions had been raised about the Syrian leader's whereabouts. Syrian state television quoted a media source denying that helicopters had fired on the capital. "The situation in Damascus is normal, but the security forces are pursuing the remnants of the terrorists in some streets," it said.
Assad's forces, who also pushed into a rebel-held district in the northerly commercial hub of Aleppo on Saturday, targeted pockets of lightly armed rebels, who moved about the streets on foot, attacking security installations and roadblocks.
Other opposition and rebel sources say the guerrilla fighters in the capital may lack the supply lines to remain there for long and may have to stage ‘tactical withdrawals'.
Residents said the shelling was so intense at dusk they could not discern the traditional cannon blast marking the end of the daily fast for the Muslim holy month of Ramadan.
On Sunday opposition activists reported fighting in Jdeidet Artouz, a suburb southwest of Damascus, 30 km (20 miles) from the occupied Golan Heights, captured by Israel in 1967. Tanks entered the suburb in the morning, they said.
Israel and Syria's other neighbors are increasingly fearful the conflict could tear through an already unstable region.
The Iraqi army sent extra border guards and officers on Sunday to the Qaim-Albu Kamal border crossing with Syria captured by the rebels on Thursday. The border was sealed by the Iraqi army on Friday, fearing a spillover in violence and Iraq's government has said it cannot help Syrians fleeing the violence.
The Syrian Observatory for Human Rights said 1,261 people had been killed across Syria since last Sunday when the fighting escalated in Damascus, including 299 of Assad's forces, making it by far the bloodiest week in an uprising that has claimed the lives of 18,000 people
A total of 180 people, including 48 troops, died on Saturday alone, many them in Homs province, epicenter of the revolt.
Most shops in Damascus were closed and there was only light traffic - although more than in the past few days. Some police checkpoints, abandoned earlier in the week, were manned again.
Many petrol stations were closed, having run out of fuel, and those that were open had huge lines of cars waiting to fill up. Residents reported long queues at bakeries.
FLIGHT FROM ALEPPO
A bloody crackdown on what began as a peaceful revolt has increasingly become an armed conflict between an establishment dominated by Assad's Alawite minority, an offshoot of Shi'ite Islam, and rebels drawn largely from the Sunni majority.
Opposition activists in Aleppo said hundreds of families were fleeing residential areas on Saturday after the military swept into the Saladin district, which had been in rebel hands for two days. Fighting was also reported in the densely-populated, poor neighborhood of al-Sakhour.
"For the first time we feel Aleppo has turned into a battle zone," a woman, who declined to be named, said by phone from the city.
On the Iraqi-Syrian border, Iraqi security and border officials said Syrian forces had reasserted control over the Yarubiya crossing point on the Syrian side of the frontier, briefly seized by rebels on Saturday.
Syrian opposition activists said several towns in Syria's Kurdish northeast had passed without a fight into local hands in recent days as central authority eroded.
The surge in violence has trapped millions of Syrians, turned sections of Damascus into ghost areas, and sent tens of thousands of refugees fleeing to neighboring Lebanon.
Regional and Western powers have voiced concern the conflict might become a full-blown sectarian war that could spill across borders. But Assad's opponents remain outgunned and divided.
Israel said the "great threat" it faced from the Syrian conflict is that the Assad government may collapse and its stock of chemical weapons and missiles fall into the hands of the Lebanese Islamist group Hezbollah.
"We certainly don't want to be exposed to chemical weapons falling into the hands of Hezbollah or some other terror groups. ... It's a great threat," Israeli Prime Minister Benjamin Netanyahu said on the U.S. "Fox News Sunday" television program.
(Additional reporting by Oliver Holmes in Beirut, Fadhil Al-Badran in Falluja, Iraq, Suleiman al-Khalidi in Hacipasa, Turkey, Igor Ilic in Brijuni, Croatia; Leigh Thomas in Paris, Jamal al-Badrani in Mosul, Iraq, Sylvia Westall in Baghdad and Jonathan Burch in Cilvegozu, Turkey; Writing by Philippa Fletcher; Editing by Giles Elgood)