BEIRUT (Reuters) - Syria's ceasefire increasingly was under threat on Sunday as the government vowed a crackdown on a wave of "terrorist attacks" and its forces shelled Homs on the day the first U.N. peace monitors entered the country.
An initial team of five U.N. ceasefire monitors arrived in the capital Damascus as expected on Sunday evening, a Reuters witness said. Ahmad Fawzi, the spokesman for international mediator Kofi Annan, said the team would be deployed on Monday.
As the monitors prepared to embark on their mission, the city of Homs, one of the hotbeds of opposition to President Bashar al-Assad, was bombarded by government forces at a rate of "one shell per minute", activists said.
Activist sources reported six people were killed on Sunday, and four bodies were found.
The observers are due to be joined by two dozen more monitors soon in line with a Security Council resolution adopted on Saturday authorizing the deployment of up to 30 people.
The Syrian government said it could not be responsible for the safety of the monitors unless it was involved in "all steps on the ground", said Syrian government spokeswoman and presidential adviser Bouthaina Shaaban.
She said Syria reserved the right to agree on the nationality of those participating.
Fawzi confirmed that the size of the mission could be expanded to 250, or perhaps somewhat more, contingent upon a second Security Council resolution that he expected would be discussed and adopted "before the end of next week".
"The mission will include civilians, political officers and human rights experts in order to observe the full implementation of the six-point plan, which includes a lot more than the cessation of hostilities," he said, referring to the peace plan brokered by Annan.
Casting further doubt on whether the ceasefire would hold, Syria said it would stop what it called "terrorist groups" from continuing criminal acts, state TV quoted a security source as saying.
"(Security forces), based on their duty to protect civilians and the country, will stop terrorist groups from continuing their criminals acts and the killing of civilians," SANA said.
"Since the announcement of an end to military operations, terrorist attacks have increased by dozens, causing a large loss of life," SANA added.
U.N. Secretary General Ban Ki-moon, speaking in Brussels, said he was concerned about the shelling of Homs and urged the Syrian government to refrain from any escalation of violence.
"As I've been stating previously, while we welcome the cessation of violence at this time I warn that the whole world is watching with skeptical eyes whether this will be sustainable.
"It is important the Syrian government takes all the measures to keep the cessation of violence. Again, I'm very concerned what happened yesterday and today when the Syrian government has been shelling the city of Homs and we have already seen some casualties.
"I urge again in the strongest possible terms that this cessation of violence must be kept."
The Arab League, which along with the United Nations backed the negotiations by Annan leading to the declaration of a ceasefire, welcomed the Security Council decision to send in monitors.
"The Arab League welcomes this decision as it represents an international will to support the mission of the joint envoy Kofi Annan," Egypt's news agency MENA said quoting deputy Arab League chief Ahmed Ben Helli.
Helli said Annan will report on his mission at an Arab League meeting on Syria on Tuesday in Qatar.
Four days after the ceasefire was meant to come into effect, violence persisted.
"Early this morning we saw a helicopter and a spotter plane fly overhead. Ten minutes later, there was heavy shelling," said Walid al-Fares, an activist living in the battered Homs district of Khalidiya.
Activist video footage, reportedly from Khalidiya, shows an explosion shortly after the sound of a missile flying through the air. Another whiz follows, and the cameraman, standing in a nearby building, pans across to show a ball of flames and smoke rising into the air.
Syrian forces killed three people in Homs after hours of heavy shelling, Rami Abdelrahman, head of the British-based Syrian Observatory for Human Rights, said. He said shells had been fired at a rate of one a minute.
"The three died in the neighborhoods of Khalidiya, Jobar and Qusour," Abdelrahman said. Clashes between armed opponents of President Assad and security forces have been reported in these districts over the past two days.
A man died from gunshot wounds in a suburb near the capital Damascus, a shepherd was killed by government loyalists in the second city Aleppo and child died from wounds in the central town of Rastan, he said.
Four other bodies were found by their families in the wider Homs and Hama provinces on Sunday, but it was unclear when they had been killed, he added.
Syria blames the violence on "terrorists" seeking to topple President Assad and has repeatedly denied journalists access to the country, making it impossible to verify the reports.
Although violence has continued throughout the ceasefire, there has been a significant drop in the daily death toll in fighting which has often killed more than 100 people a day.
Abu Rabea, an activist in Homs, dismissed the ceasefire and the monitoring mission. "Nothing has changed in Homs, government loyalists on roofs are using heavy machineguns to shoot us and we are being shelled.
"The only thing that has changed is that Kofi Annan's plan is said to be accepted by the regime and the world believes them."
Additional reporting by Louis Charbonneau and Michelle Nichols at the United Nations, Stephanie Nebehay in Geneva, John Irish in Paris, Robert-Jan Bartunek in Brussels and Yasmine Saleh in Cairo; Writing by Oliver Holmes; Editing by Michael Roddy