DAMASCUS: Syria's army launched a new wave of raids to crush resistance on Wednesday, a day after more than 60 people were killed and a UN convoy came under a bomb attack for the second time in less than a week.

The Syrian Observatory for Human Rights said at least four people died in the latest violence, all of them in the south where troops killed three people including a child when they fired on a refugee camp.

The Observatory's Rami Abdel Rahman told AFP that the camp in southern Daraa province houses Palestinian refugees and Syrians displaced from the occupied Golan Heights.

Blasts and heavy gunfire were also reported in the city of Daraa, cradle of a 15-month uprising against the regime of President Bashar al-Assad.

In the northwest, Khan Sheikhun had come under heavy machinegun fire since the morning, the Observatory added, after reporting regime forces “massacred”20 people during a funeral procession in the Idlib province town on Tuesday.

During the funeral, a convoy of UN truce observers had come under bomb attack in Khan Sheikhun, damaging three vehicles but causing no casualties, the United Nations said.

The blast occurred as the convoy made its way along a narrow street, according to reports by the Observatory, activists, and the rebel Free Syrian Army.

Video uploaded to YouTube by activists showed a convoy of UN vehicles surrounded by dozens of people before a blast was heard and a puff of smoke went up in front of the leading UN-marked jeep.

It was unclear if there were any casualties, and the vehicle drove away despite damage to its hood, according to the footage, whose authenticity could not be verified.

Activists said the UN convoy had come under attack and one car was hit by a shell, prompting the monitors to quickly leave the area.

Major Sami al-Kurdi, a spokesman for the Free Syrian Army, told AFP the monitors had arrived during the funeral and that their presence had encouraged more mourners to turn out and join the procession.

“The regime dared to attack the procession, however, and then targeted the vehicles of the UN observers from a regime checkpoint,” he said.

It was the second roadside bombing involving the observers' vehicles in less than a week, after a blast wounded six Syrian soldiers escorting a UN convoy in Daraa city on May 9.

The United Nations, which accuses both sides of violating an April 12 ceasefire, reaffirmed its condemnation of any violence against the monitors.

“This mission is there to help the people of Syria, to help ensure that the six-point plan is implemented,” spokesman Martin Nesirky said, referring to a peace plan drawn up by UN-Arab League envoy Kofi Annan.

“Anything that interrupts their work and endangers the lives of UN personnel is something we would condemn.” The Observatory, which is based in Britain, updated its toll of people killed in Syria on Tuesday to 64, including two rebel fighters and 11 regular army soldiers.

The bloodshed comes despite a truce brokered by Annan as part of a six-point plan aimed at ending violence that has swept Syria since March 2011.