(Adds fighting in south; Syria replies to Annan)
* Annan considers answers from Assad to peace bid
* Syrian forces hit rebels next to Jordan border
* China offers aid, Wen says not taking sides
* Assad calls parliamentary election; U.S. calls it "ridiculous"
By Khaled Yacoub Oweis
AMMAN, March 14 (Reuters) - Heavily armed forces loyal to President Bashar al-Assad battled rebels in the southern city of Deraa on Wednesday, while U.N. envoy Kofi Annan considered Syria's response to plans aimed at ending the violence.
Around 20 tanks and armoured vehicles surrounded the al-Balad district of Deraa, on the border with Jordan, and fired anti-aircraft guns into buildings, activist Rami Abdelhaq said from Deraa, where the revolt against Assad began a year ago.
Annan visited Damascus at the weekend and gave the Syrian president what he termed "concrete proposals" aimed at restoring peace. Assad's response had been received and Annan was studying it, his spokesman Ahmad Fawzi said.
"The envoy has received a reply from President Assad. He will have more to say later today," Fawzi said from Geneva.
Since the former U.N. chief's visit, the violence has continued unabated, with Syrian forces pounding built-up areas around the northern city of Idlib, in the central city of Homs and in the south, around Deraa.
"The attack began early this morning. The rebels are firing back, but they are outgunned," said Abdelhaq, speaking by phone, with the sound of heavy gunfire echoing in the background.
A U.N. official has said more than 8,000 people have died in the uprising and the U.N. refugee agency said on Tuesday that some 230,000 Syrians had fled their homes during the past 12 months, of whom around 30,000 have sought safety abroad.
In an apparent bid to deter the exodus, Syrian forces have laid landmines near its borders with Lebanon and Turkey along routes used by refugees to escape the mayhem, advocacy group Human Rights Watch said.
Looking to show the world that it was pressing ahead with a reform programme, the Syrian parliament said on Tuesday that Assad had ordered a legislative election for May 7.
It will be held under a new constitution, approved by a referendum last month which the opposition and their Western and Arab backers dismissed as a sham.
Russia and China have welcomed Assad's reform pledges, including the promised election, and have blocked moves in the United Nations to censure the Syrian leader.
Chinese Premier Wen Jiabao said on Wednesday that Beijing was taking no sides in the crisis, and that he was "deeply pained" by the suffering of the Syrian people, though his remarks did not suggest China's diplomatic position will change.
Earlier, state media said China will offer $2 million in humanitarian aid through the Red Cross.
Russian Foreign Minister Sergei Lavrov said on Tuesday that Syrian government forces would not stop fighting or withdraw from their positions unless rebel forces instantly mirrored their move.
The U.S. State Department was dismissive of Assad's election plan: "Parliamentary elections for a rubber-stamp parliament in the middle of the kind of violence that we're seeing across the country? It's ridiculous," spokeswoman Victoria Nuland said.
After a crackdown in the central city of Homs, the army has intensified its operations in the north and has been shelling the town of Idlib for the past three days.
An activist in the town, speaking by telephone, said on Tuesday security forces had killed more than 20 people trying to leave the area in the past two days and dumped their bodies in al-Bilal mosque. When locals went to inspect the corpses, they too came under fire, pushing the death toll above 50, he said.
Another activist gave a slightly lower death toll.
"When people came from the neighbourhood early this morning, the security forces also started firing at them. In total, about 45 people were massacred," said the man, who like many in Syria gave only his first name, Mohammed, for fear of reprisals.
Reports from Syria cannot be independently verified as the authorities deny access to rights groups and journalists.
The United Nations said on Tuesday that it would soon deploy human rights monitors in countries bordering Syria to collect eyewitness testimony on atrocities committed in the country.
Syria lies in a pivotal position, bordering Turkey, Jordan, Israel, Iraq and Lebanon. Its 23-million population comprises a mix of faiths, sects and ethnic groups, and analysts say the gathering conflict could destabilise the entire region.
On Tuesday, the Organisation of Islamic Cooperation (OIC), the world's largest Islamic body, said it had received permission by Damascus to send humanitarian aid to Syria, and will send a team there soon to assess the population needs. (Writing by Crispian Balmer; Additional reporting by Ben Blanchard in BEIJING and Yasmine Saleh; Editing by Daniel Magnowski and Michael Perry)