The president of Ukraine, Petro Poroshenko, has called his military officials to an emergency meeting after a rocket attack killed at least 30 people and wounded 86 in the eastern port of Mariupol.

The attack came after a separatist leader announced a new offensive in the city.

Rebels say they will reject all peace deals with the Ukrainian government.

Director of Medecins Sans Frontieres Ireland Jane-Ann McKenna says it is almost impossible to calculate the exact death toll from today's violence:

The Interior Ministry said homes were alight and the mobile phone network had gone down after pro-Russian separatists fired long-range rockets on the port city of Mariupol in the region of Donetsk.

The attack comes after rebels threatened to increase their campaign triggering an escalation of violence in a country where a shaky cease-fire is struggling to hold.

Pro Russian separatist leader Alexander Zakharchenko said the attack was the start of an offensive on the city.

It came the day after he said he was ripping up the September peace agreement and launching an all-out offensive aimed at seizing lands.

He was quoted by a Russian news agency as saying at a memorial service for eight civilians killed at bus stop: "Today an offensive was launched on Mariupol. This will be the best possible monument to all our dead."

Mariupol mayor Yuriy Khotlubei said in a video statement: "The shelling was carried out by militants. This is very clearly Russian aggression that has caused terrible losses for the residents of the eastern part of our city."

The authorities in the government-held city struggled to calm the panicking residents and condemned the attack on ordinary residents.

One resident said: "Obviously everyone in the city is very scared. The rebels have already seized the airport and now they are starting to destroy Mariupol itself."

Footage and pictures emerging from the city showed widespread damage.

A peace deal between the government and the separatists was signed in September but is has been repeatedly violated by both sides. It came after a push on the city of Mariupol in August.

There has been a significant increase in fighting in the last two weeks and the United Nations says 262 lives have been claimed in the past nine days alone.

Jane-Ann McKenna said many civilians have been cut off from aid:

Originally posted at 12.15pm