There has been fresh shelling near the airport in Donetsk, following overnight attacks in Mariupol, raising fears that the 36-hour-old ceasefire in eastern Ukraine is near to collapse, reports GHN based on BBC.
The truce, agreed on Friday, had been holding for much of Saturday.
But strong explosions were heard on the outskirts of Donetsk, the main rebel-held city in the east, early on Sunday.
Overnight, there was heavy shelling of Ukrainian government positions in the port city of Mariupol.
Before the ceasefire was agreed on Friday, the separatists had been advancing on both Donetsk airport and Mariupol, a key city on the route to Crimea and an economic prize for any possibility of independence for the eastern Ukraine region.