Updated at 7:13 a.m. ET
(AP) BEIRUT - Syrian troops clashed with army defectors in an eastern city Thursday, leaving at least one person dead, while government forces bombarded rebel-held neighborhoods of the central city of Homs, activists said.
The renewed violence comes as the international community struggles to salvage a week-old cease-fire that is seen as the only way to end the bloodshed that has killed more than 9,000 people since an uprising against President Bashar Assad began 13 months ago.
U.N. Secretary-General Ban Ki-moon acknowledged that violence has escalated in recent days after a lull on April 12, the day the cease-fire went into effect, but he said peace efforts must continue.
"I remain deeply concerned about the gravity of the situation in the country," he said in a letter late Wednesday to the U.N. Security Council. "However, without underestimating the serious challenges ahead, an opportunity for progress may now exist, on which we need to build."
The Security Council has authorized an advance team of 30 observers to monitor compliance with the peace plan put forth by international envoy Kofi Annan, and a small group is already at work.
Ban called on the council to approve an expanded United Nations Supervision Mission in Syria, to be known as UNSMIS, comprising an initial deployment of up to 300 military observers in approximately 10 locations throughout the country, for an initial period of three months.
On Wednesday, Syrian security forces opened fire on anti-regime demonstrators surrounding the cars carrying some of the observers in a Damascus suburb, sending them speeding off and protesters dashing for cover, according to activists and amateur videos. The observers escaped unharmed.
The Britain-based Syrian Observatory for Human Rights said clashes broke out Thursday in Deir el-Zour, near the border with Iraq, killing one civilian and wounding three others.
Syrian troops also began shelling the rebel-held neighborhoods of Qarabees and Jouret el-Shayah in Homs which has emerged as a center of the rebellion about 6:30 a.m. and intense shooting and explosions could be heard for hours, according to the Observatory.
"We are being subjected to intense shelling with mortars," Abu Joud, an activist in the city, said via Skype. The activist urged international observers, who began their mission in Syria this week, to visit Homs.
"Until now they haven't come here although Homs is the hardest hit city in Syria," Abu Joud said.
Amateur videos posted online showed smoke billowing from a residential area in Homs as the sound of shelling could be heard. "This is the destroyed Homs. Homes are on fire and people fled. May God help us. Look Kofi Annan," an activist could be heard saying.
Activists also said Syrian troops were shelling areas in the nearby town of Qusair, near the border with Lebanon. The Observatory and the Local Coordination Committees, another activist group, said the regime was sending reinforcements to the town. Rebels have had control of some areas of the town for months.
"A shell is falling every five minutes on Qusair," said Rami Abdul-Rahman who heads the Observatory.
Assad's regime has strictly limited reporting in the country so the reports could not be independently confirmed.