Activists say pro-government forces have penetrated an opposition bastion east of Damascus in a swift advance that threatens to disrupt a years-long stalemate around the Syrian capital.

The Britain-based Syrian Observatory for Human Rights monitoring group said Thursday that government forces, backed by airstrikes, ground-to-ground rockets and the allied Lebanese Hezbollah militia, seized a portion of the eastern Ghouta suburbs near Damascus airport, displacing hundreds of families.

The activist Local Coordination Committee network says pro-government forces seized the town of Deir al-Asafir, an iconic opposition stronghold that has asserted its autonomy since 2012.

Syrian state media says the army seized other villages in the region.