(QHA) -

European Union foreign ministers are due to hold an emergency meeting on Thursday to discuss the EU’s response to an assault by Russian-backed rebels on the southeastern Ukrainian city of Mariupol, EU Foreign Affairs Chief Federica Mogherini said on Twitter on Sunday.

The ministers will likely discuss whether to tighten sanctions against Russia for the attack, which killed dozens of civilians on Saturday in the strategically important port city on the Sea of Azov, officials said.

German Foreign Minister Frank-Walter Steinmeier over the weekend said in response to the attack that governments need to know more about whether Moscow is trying to rein in the rebels or not.

Mariupol is near territory controlled by the rebels in the Donetsk and Luhansk provinces of eastern Ukraine, but Ukrainian forces have managed to retain control of the city since fighting in the country erupted nearly a year ago.

The attack came a day after the pro-Russian separatists announced they were pulling out of peace talks and launching a new offensive.