Smoke rises after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad near Aleppo's Sheikh Najjar Industrial City, on March 5, 2014. Picture: Ammar Abdullah

Damascus - Five people were killed and more than 20 wounded on Thursday in a bomb blast near a security headquarters in central Syria's city of Hama, a monitor said.

“A truck packed with explosives detonated... near a branch of the military intelligence, killing at least five people and injuring more than 20,” the Syrian Observatory for Human Rights said.

Syrian state television also reported the blast, saying four people were killed and 22 wounded in a “terrorist explosion” at the southern entrance of the city.

In the northern province of Raqa, two suicide bombers blew themselves up inside Base 17, an army base under siege by opposition forces, according to the Observatory, a Britain-based group that relies on activists and other witnesses inside Syria.

The group said two fighters from the jihadist Islamic State of Iraq and the Levant had blown themselves up at the headquarters, which is north of the group's stronghold in Raqa's provincial capital.

Clashes between regime forces and ISIL broke out after the blasts, which the Observatory said killed several soldiers.

In western Idlib province, fierce clashes raged around the town of Morek on the strategic road between Hama and Idlib, which the army needs in order to supply a base in the province.

The army has been trying to capture Morek and secure the road, but the Observatory said rebels had launched a preemptive attack to seize another point on the road - Khan Sheikhun - enabling them to block the route even if Morek fell.

The Observatory said 15 soldiers were killed in fighting on the road on Wednesday and overnight, adding that regime aircraft were bombing the area around Khan Sheikhun on Thursday.

In Damascus, meanwhile, the group said a man died after regime shelling on the Palestinian Yarmuk camp on Wednesday, where a ceasefire has broken down.

The renewed fighting has halted aid deliveries to the besieged camp, where two more people died from lack of food and medical care on Wednesday, the Observatory said.

Around 130 people are reported to have died because of shortages in the camp caused by the army siege.

In Damascus province, regime planes renewed raids on the outskirts of Yabrud, the last rebel stronghold in the Qalamun region near the border with Lebanon.

The Observatory reported eight air raids on the area, which regime troops are trying to recapture.

More than 140 000 people are estimated to have been killed since the start of the uprising against President Bashar al-Assad in March 2011. - AFP