BEIRUT, Lebanon — Syrian opposition activists said Sunday that government forces had killed at least 80 people in a town south of Damascus, and then carried out mass arrests as the residents tried to bury the bodies.

Residents in the town, Jdaidet al-Fadl, and activists described a three-day campaign in which soldiers from the army and loyalist militias systematically burned houses, arrested men, took over field hospitals and killed the wounded.

The state news agency SANA gave a somewhat different account: “Armed forces units inflicted heavy losses upon terrorists in the town of Jdaidet al-Fadl in the Damascus countryside, injuring a number of them and killing others.”

Neither version of events could be independently confirmed.

The town is near a military base along a corridor connecting the city of Dara’a with two southern suburbs of Damascus — Daraya and Moadhamiya — that have been hotly contested. Rebels have hung on in the two suburbs through months of withering shelling and airstrikes.