Reports from eastern Ukraine say seven people were killed overnight in fighting along the front lines between government forces and pro-Russian separatists in eastern Ukraine -- including an intense artillery duel at the southeastern Ukrainian city of Mariupol.

Residents describing the battle as the heaviest fighting there in more than three months.

Correspondents say the fighting on August 17 was between government forces on the eastern side of Mariupol and artillery positioned to the east of the city in territory under the control of pro-Russian separatists.

Reports say houses were destroyed in the village of Sartana about 20 kilometers east of Mariupol, and that an oil depot has also been damaged.

Regional police in Mariupol said that two civilians -- a man and a woman -- were killed by separatist shells that landed in Sartana.

Separatists said at least three people were killed by government shelling of Horlivka, a hot spot northeast of Donetsk.

There also were reports of heavy shelling by government forces into separatist-controlled Donetsk early on August 17.

Donetsk city officials say at least two people were killed by shells that exploded withing the administrative center of Donetsk.

Russian Foreign Minister Sergei Lavrov said in Moscow on August 17 that recent developments in eastern Ukraine suggest Kyiv may be preparing to renew large-scale fighting.

The latest violence comes after a week of intensifying clashes between Ukrainian forces and pro-Russian separatists near the government-held coastal city on the Sea of Azov.

Germany’s Foreign Minister Frank-Walter Steinmeier warned on August 16 that the situation in eastern Ukraine is "explosive," saying urgent talks are needed to prevent "a new military escalation spiral."

Steinmeier made the comments in an interview published in the German newspaper Bild am Sonntag.

He said he has proposed that representatives of Kyiv and the Russia-backed separatists in eastern Ukraine meet immediately with representatives of the Organization for Security and Cooperation in Europe (OSCE) for talks on reducing tension.

A cease-fire deal signed in Minsk in February has eased the violence somewhat since early in 2015.

But clashes have been occurring with increasing frequency during the past week with both sides accusing each other of violations on a daily basis.

Much of the fighting has been along a key road linking Mariupol with the separatist-controlled city of Donetsk to the north.

Mariupol sits along a strategic coastal route linking Russia and separatist-controlled parts of eastern Ukraine with Crimea, which was illegally annexed by Russia in March 2014.

Ukraine's government also accuses Russia of deploying Russian military forces within eastern Ukraine to support the pro-Russian separatists.

It also has accused Russia in the past of firing artillery and rockets from Russian territory at government-held positions on the eastern edges of Mariupol.

Despite mounting evidence to support the allegations, Russia continues to deny having any direct military role in the confict,

More than 6,400 people have been killed in eastern Ukraine since fighting broke out there in April 2014.

With reporting by Reuters, BBC, Interfax, TASS, and Bild am Sonntag