Indiscriminate rocket fire has hit a market, two schools, homes and shops in the eastern Ukrainian city of Mariupol, killing at least 29 people.
Ukraine’s top rebel leader said an offensive had begun on the strategically important port.
The attack came a day after the rebels rejected a peace deal and said they were going on a multi-prong offensive against the government in Kiev to vastly increase their territory.
The rebel stance is upending European attempts to mediate an end to the fighting in eastern Ukraine, which the UN said has killed nearly 5,100 people since April 2014.
Mariupol, which lies on the Azov Sea, is the major city between mainland Russia and the Russia-annexed Crimean Peninsula.
Heavy fighting in the region in the autumn raised fears that Russian-backed separatist forces would try to take over the government-held city to establish a land link between Russia and Crimea.
Ukrainian rebel leader Alexander Zakharchenko said an offensive had begun on Mariupol, the RIA Novosti news agency said.
He spoke as he laid a wreath where at least eight civilians died when a bus stop was shelled in Donetsk, the largest rebel-held city in eastern Ukraine.
Rebel forces have positions within 10km from Mariupol’s eastern outskirts.
Ukraine’s defence ministry said there were three separate strikes from Grad multiple-rocket launchers today on Mariupol and surrounding areas.
“The area that came under attack was massive,” Mariupol mayor Yuriy Khotlubei said.
“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.”
Shortly after the attack, local authorities said around 10 people had died, but by the evening, Mr Khotlubei announced the death toll had risen to 29.
Kiev blamed the attack on separatist rebels and the Russian military. Prime Minister Arseny Yatseniuk condemned the incident as a deliberate attack on peaceful citizens by the rebels, but said the real threat lay beyond separatist territories. “The world needs to stop the Russian aggressor threatening
Ukraine, Europe and global security .. The problem is in the hero-town of Moscow - Kremlin, Vladimir Putin," he said at a meeting of security and defence chiefs.
A Ukrainian military checkpoint on a road out of the city toward rebel-held areas was also hit and one serviceman was killed, the defence ministry said.
Mariupol city council urged residents not to panic and to ignore rumors that Ukrainian armed forces were planning to withdraw.
“On the contrary, all units are on fully battle-ready. Security measures in the city have been strengthened,” the council said in a statement.
No armed separatist units have been noted moving toward the city, the statement added.
Responding to the attack upon Mariupol, EU foreign affairs chief Federica Mogherini called on Russia to use its influence over the separatist leaders to halt their offensive and to desist from providing military and financial support.
Russia insists it does not support the rebels, but Western military officials say the sheer number of heavy weapons under rebel control belies that claim.
Clashes were taking place across the eastern regions of Donetsk and Luhansk, where separatist insurgencies emerged in April following Russia’s annexation of Ukraine’s Crimean Peninsula.
Fighting has also been intensifying recently for the government-held town of Debaltseve, 50km east of Donetsk. Main roads into the town are under separatist control and it’s feared that Ukrainian forces stationed there could soon be fully surrounded.
A peace deal signed in September in the Belarusian capital of Minsk envisaged a cease-fire and a pullout of heavy weapons from a division line in eastern Ukraine.
It has been repeatedly violated by both sides, and heavy artillery and rocket barrages have increased the civilian death toll in the last few weeks.
Foreign ministers from Russia, Ukraine, France and Germany agreed on Wednesday to revive that division line, but fighting has continued unabated.
On Thursday, mortars rained down on Donetsk, hitting a bus and killing several bystanders. Rebel officials said 13 were killed in that attack. Monitors from the Organisation for Security and Cooperation in Europe (OSCE) cited city mortuary officials as saying eight bodies were received.
On January 13th, a bus parked near an army checkpoint north of Mariupol was hit by a shell, resulting in the death of 13 people. Ukraine blamed the rocket attack on separatists.
The OSCE’s special monitoring mission in eastern Ukraine condemned the growing number of civilian casualties and called today for restraint from all sides.
Agencies