Syrian troops shelled and then stormed the village of Treimsa in the central province of Hama, monitors and activists said on Thursday, as at least 45 people were killed across the strife-torn country.

"Regime forces pounded Treimsa... using tanks and helicopters," said the Britain-based Syrian Observatory for Human Rights, adding that soldiers later stormed the besieged village.

The Observatory said eight civilians and one Free Syrian Army rebel were killed in Hama. The Syrian Revolutionary General Commission reported that one of the Treimsa victims was a doctor shot dead while trying to help the wounded.

"The village school was totally destroyed," a Hama-based activist calling himself Abu Ghazi told AFP via Skype. "Every month, there is a major attack somewhere in Hama province, while arbitrary detentions happen every day," the activist said.

With Idlib in the northwest, Homs in the centre and much of the countryside of Aleppo in the north "out of control, the regime is trying to keep Hama on its side." "Hama is in the centre of Syria, and is a link in a chain of provinces where anti-regime feeling is strong; the regime will do anything to keep it controlled."

In the central province of Homs, eight people were killed on Thursday, the Observatory said. "The situation here is very bad," said an activist in Homs city who identified himself as Abu Bilal. "We need humanitarian organisations to move. We have scores of injured. We've been under siege for 35 days."

The siege by regime forces of several rebel-held districts of Homs "is worse than the siege of Gaza. At least in Gaza, people tried to break the siege. We've lost hope in all the world." Despite two attempts, the Red Crescent and International Committee of the Red Cross were unable in late June to reach the wounded in Homs.

"All parties to a conflict must respect the lives of civilians, and that includes the right of civilians to leave and go to safe areas," ICRC spokesperson Rabab al-Rifai said on Thursday, adding that negotiations to enter besieged areas of Homs were "ongoing."

The Observatory confirmed a total of 45 deaths -- 29 civilians, 11 soldiers and five rebels -- across the country on Thursday.It has said more than 17,000 people have been killed since the uprising erupted in mid-March last year. It is not possible to independently verify death tolls. The United Nations stopped compiling such figures at the end of 2011.