At least 30 people were killed and scores injured in a series of rocket attacks in the city of Mariupol in east Ukraine.
According to the BBC, Ukraine blamed pro-Russia rebels, but the separatists said Ukrainian forces were behind the attacks.
A prominent pro-Russian leader initially claimed responsibility for the offensive against Mariupol on Saturday, but later backtracked saying that he would not storm the city.
The Organisation for Security and Co-operation in Europe (OSCE) said the rockets were fired from rebel-held areas.
But Alexander Zakharchenko, leader of the self-proclaimed Donetsk People's Republic, said his forces had not carried out "active operations" near Mariupol until Saturday, adding that he ordered his troops to "neutralise" the positions of Ukrainian troops east of the port city after Kiev blamed the rebels for the attack, the report said.
