President Petro Poroshenko said Sunday that his government was committed to de-escalating the fighting in eastern Ukraine, following a surge in violence in recent days.

"Ukraine remains a firm proponent of a peaceful solution," he told an emergency meeting of security and defense chiefs.

"Beginning a political process of de-escalation and regulation remains our priority. We don't see an alternative to the Minsk agreement."

The ceasefire deal signed with pro-Russian separatists in the Belarusian capital on September 5 has repeatedly been breached. Renewed fighting over the past week escalated on Saturday with a deadly rocket attack on the government-held port city of Mariupol. At least 30 people were killed and more than 90 injured in the attack, which came one day after the rebels ruled out future peace talks with Kyiv.

Investigators from the Organization for Security and Cooperation in Europe (OSCE) confirmed the attack had been launched from territory controlled by the separatists, although rebel leader Alexander Zakharchenko has rejected responsibility for the civilian deaths.

Poroshenko said European Union foreign ministers would meet on Monday to discuss the crisis and to "coordinate steps for improving Ukraine's security and upping the pressure on Russia." He added that Kyiv planned to lobby for harsher sanctions on Russia for its alleged role in providing the rebels with military and financial support - charges Russia has denied.

Russian Foreign Minister Sergei Lavrov said on Sunday, in a conversation with his US counterpart John Kerry, that Moscow was prepared to "do everything in its power to encourage parties towards a peaceful solution." He also blamed Ukrainian government forces for the most recent fighting.

More than 5,000 people have been killed since fighting broke out in eastern Ukraine in April 2014.

International condemnation

People lay flowers in Kyiv's Independence Square for the victims of the Mariupol attack

The attack on Mariupol was met with widespread international condemnation. United States President Barack Obama said that he was deeply concerned by the latest break in the ceasefire.

The European Union's foreign policy chief, Federica Mogherini, called on Russia to intervene to stop the fighting. United Nations Secretary-General Ban Ki-moon said peace needed to be "urgently restored."

On Saturday, Russia used its veto power to block the Western-backed UN Security Council from condemning the Mariupol shelling, as tweeted by Britain's UN ambassador Mark Lyall Grant.

The UN draft statement called for "an immediate de-escalation of violence," employment of the September 5 truce between Kyiv and pro-Russian rebels and an "objective investigation" into the rocket attack on Mariupol.

Moscow said Britain's insistence that rebel "self-defense forces" were being backed by Russia was their reason for not backing the document.

nm/bw (Reuters, AFP)