At least 15 people died today when rockets hit a market in a vital port linking Ukrainian rebel lands with Russian-occupied Crimea after the pro-Moscow insurgents vowed to grab more land.
Ukrainian interior ministry said 46 people were wounded in the city of Mariupol when Grad rockets hit a large residential district facing roads that have come under attack from separatist militias in recent days.
The local mayor's office added that several buildings went up in flames and cars were torched in the morning assault.
"Right now there are problems with the cell phone network so it is impossible to call relatives who live in that part of town," Mariupol resident Eduard told AFP by telephone.
"Obviously, everyone in the city is very scared. The rebels have already seized the airport. And now they are starting to destroy Mariupol itself."
Photographs of the attack published on a local news site showed a towering cloud of grey smoke billowing over family homes and a row of high-rise apartment buildings.
The southeastern Sea of Azov city of nearly 500,000 sits on a highway connecting guerrilla-held regions to the east and the Black Sea peninsula of Crimea that Russia annexed from Ukraine in March in a move condemned by the international community.
A rebel assault on the port in August saw Kiev repel the attack at a heavy cost that prompted Ukrainian President Petro Poroshenko to agree to a September 5 truce.
That deal was followed by still more clashes that killed at least 1,500 people and was ultimately rejected by the rebels yesterday.
The separatist leader of Donetsk said yesterday he was ripping up the September agreement and launching an all-out offensive aimed at seizing lands currently under the control of the pro-Western authorities.
"Our side will no longer push for any more truce talks," Alexander Zakharchenko said.
"We are going to advance to the very border of Donetsk province," he added in reference to areas of the heavily Russified region still under government control.
There was no immediate comment on the battle from top rebel commanders.
But an unnamed separatist "defence ministry" source denied any involvement to a pro-Russian website.
"The militias did not open fire on Mariupol -- especially its residential districts," the unidentified militant told the Donetsk News Agency.
