Firefighting has been reported near Donetsk airport while shelling is being heard in the city of Mariupol where one civilian was killed early Sunday just two days after a cease-fire was signed, local officials said.
A woman has died in hospital as a result of overnight shelling in Mariupol, making hers first death since the ceasefire came into force on Friday.
A spokesman for Ukraine's National Security Council, Volodymyr Polyovyi, 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.
Reuters cited an unnamed Ukrainian officer saying there has been an artillery attack on Mariupol, which Kiev forces are occupying at the moment.