Reuters witnesses heard renewed artillery shelling to the east of the port of Mariupol in eastern Ukraine on Friday, Sept 5 hours before Ukrainian, Russian and European envoys are expected to back a peace plan and a ceasefire, the news agency reported.

"Our artillery has come and is being deployed against the (pro-Russian) activists," the mayor of Mariupol, Yuri Khotlubey, told Ukraine's 112 TV channel.

A commander of a Ukrainian volunteer militia based in Mariupol told Reuters: "We were under fire all night but we are still keeping the pro-Russian activists at bay. They are facing us with tanks and artillery."