A civilian has been killed in shelling in the Ukrainian port city of Mariupol, raising fears that a ceasefire signed two days ago is on the verge of collapse.
The fatality was reported on the same day that large explosions were heard near the airport in Donetsk.
Blasts from the area near the airport were powerful enough to be heard in downtown Donetsk, the main rebel-held city in eastern Ukraine.
Volodymyr Polyovyi, a spokesman for Ukraine's national security council, said at a briefing in Kiev that rebels appeared to have tried to attack the airport, which has been under the control of government troops since May and has come under unremitting attacks from pro-Russia separatist rebels since then.
The ceasefire had appeared to be holding for much of yesterday but shelling started late at night.
A rebel statement said Ukrainian forces violated the ceasefire by firing on their positions in six locations yesterday, including near Donetsk airport. The statement said several rebels were killed.
Shelling also occurred overnight on the outskirts of Mariupol, where Ukrainian troops retain defensive lines against the rebels.
The city council there said one civilian was killed and a serviceman was wounded.
A shell also destroyed a nearby petrol station and the volunteer Azov Battalion said on Facebook that their positions were hit by Grad rockets, but did not give details.
Mariupol is located on the coast of the Sea of Azov, 70 miles south of Donetsk.
Rebels recently opened a new front on the coast, leading to fears that they were trying to secure a land corridor between Russia and the Crimean Peninsula, which Russia annexed in March.
Ukraine, Russia and the Kremlin-backed separatists signed the ceasefire deal in Belarus capital Minsk on Friday in an effort to end more than four months of bloodshed.
The negotiators also agreed on the withdrawal of all heavy weaponry, the release of all prisoners and the delivery of humanitarian aid to devastated cities in eastern Ukraine.
Western leaders voiced scepticism over Russia's commitment to the deal.
A previous 10-day ceasefire, which each side repeatedly accused the other of violating, yielded few results at the negotiating table.
Ukrainian president Petro Poroshenko's office said yesterday he and Russian president Vladimir Putin had discussed steps "for giving the ceasefire a stable character" in a telephone conversation.
But, it said, both leaders assessed the ceasefire as having been "fulfilled as a whole."
Fighting between pro-Russian rebels and Ukrainian government troops has ravaged the already-teetering Ukrainian economy, claimed at least 2,600 civilian lives and left hundreds of thousands homeless, according to United Nations estimates.