Rebels launch major rocket assault on crucial Ukraine port

A top pro-Russian rebel has announced the launch of a major offensive on Ukraine's government-held port of Mariupol, confirming responsibility for rocket fire that killed at least 27 people.

"Today, we launched an offensive against Mariupol," Russia's RIA Novosti news agency quoted Donetsk separatist leader Alexander Zakharchenko as saying.

"This will be the best tribute possible for all our dead."

The rocket attacks were launched overnight after Russian-backed rebels rejected peace talks, the Mariupol mayor's office said.

"The shelling killed 27 people and wounded more than 90 people," Oleg Kalinin, a spokesman for the mayor's office said, adding that the figure could rise as authorities conduct search operations.

The office said several buildings went up in flames and cars were torched in the attack that saw Grad rockets smash into a packed residential district.