A Syrian activist group says heavy fighting has erupted between rebels and government troops in the capital.

The Britain-based Syrian Observatory for Human Rights says the fighting started Sunday and continued into Monday in the Damascus neighborhoods of Tadamon and Yarmuk, which is near a Palestinian refugee camp.

Activists say government jets have bombarded several other Damascus enclaves.

Syria's fractured opposition factions began key talks Sunday aimed at forming a united front to gain international recognition and bolster their chances to oust President Bashar al-Assad.

The first four days of meetings in the Qatari capital, Doha, are focused on transforming the Syrian National Council, the largest opposition group outside Syria, into a representative government-in-exile.

SNC leaders said the group is expected to expand from about 200 members to 400.

A separate meeting of the wider opposition movement in Doha aims 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.