A Syrian activist group says a suicide car bomber has killed more than 50 Syrian soldiers and gunmen loyal to President Bashar al-Assad in central Hama province.

The head of the Britain-based Syrian Observatory for Human Rights, Rami Abd al-Rahman, said Monday's attack in the village of Ziyara was carried out by the Al-Nusra Front, an al-Qaida-inspired Islamist militant group.

The death toll could not be independently verified.

The Observatory also said heavy fighting that began Sunday between rebels and government troops in the capital, Damascus, has continued near a Palestinian refugee camp. Palestinian and official Syrian sources said more than 30 people were killed in a 24-hour period.

Activists also said at least 20 Syrian rebel fighters were killed in an air strike in northwest Idlib province.

Also Monday, the main Syrian opposition bloc, the Syrian National Council, voted to broaden its ranks to include more activists and political groups from inside the country in the face of U.S. pressure to create a more representative leadership that could work with the West.

Washington and other foreign backers say they cannot boost aid to Syrian rebels unless the opposition is united and represents more diverse groups within Syrian society, including those fighting on the ground in Syria.

Syria's fractured opposition factions began talks Sunday in the Qatari capital, Doha.

Later in the week, a separate meeting of the wider opposition movement will aim to form a united coalition that includes rebel fighters and others inside Syria.

The Syrian conflict is entering its 20th month and has caused the deaths of an estimated 36,000 people.