Explosions reported on outskirts of rebel-held city in Ukraine

Reports raise new fears cease-fire is on the verge of collapse.

DONETSK, Ukraine — Strong explosions were heard early Sunday on the outskirts of the main rebel-held city in eastern Ukraine near the airport, raising new fears that a cease-fire signed two days ago is on the verge of collapse.

The airport in Donetsk has been under the control of government troops since May and has come under steady attack from pro-Russia separatist rebels since then.

The cease-fire had appeared to be holding for much of the day on Saturday, but shelling took place on the edge of the port city of Mariupol late at night.

Heavy explosions were reported to be coming from the city’s eastern outskirts, where Ukrainian troops retain defensive lines against the rebels.

The city council said one serviceman was wounded when a checkpoint was hit.

Ukraine, Russia and the Kremlin-backed separatists signed the cease-fire deal in the Belarusian capital Minsk on Friday in an effort to end more than four months of bloodshed in the region.

The negotiators also agreed on the withdrawal of all heavy weaponry.