A refugee camp in Daraa province which houses Palestinian refugees and Syrians displaced from the occupied Golan Heights were raided by Syrian forces on Wednesday, the Syrian Observatory for Human Rights reported.

Blasts and gunfire were also heard early Wednesday in Daraa city, the Observatory said in a statement, without giving further details.

Regime forces also killed a young man in during a raid on Mleiha al-Aatsh village in Daraa province, the Britain-based watchdog said. Six men were arrested during the raid, the statement added.

Khan Sheikhun in northwestern Idlib province has been under heavy machinegun fire since the morning, the Observatory said, a day after it reported regime troops "massacred" 20 people during a funeral procession in the town.

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

The watchdog 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 UN-Arab League envoy Kofi Annan as part of a six-point plan aimed at ending violence that has swept Syria since March 2011, when the uprising against President Bashar al-Assad began.

The United Nations has accused both sides to the conflict of violating an April 12 ceasefire and warned that the country is edging closer to full-blown civil war.

More than 12,000 people, the majority of them civilians, have died since the Syrian uprising began, according to the Observatory, including more than 900 killed since the truce came into effect.