Ukraine warns of escalation in fighting around Mariupol

Ukraine on Sunday warned of a possible escalation in fighting around the besieged southern port city of Mariupol after Moscow said it was focusing its military resources on capturing the eastern Donbas region.

"This means a potential or sharp deterioration around Mariupol," an adviser to the head of the President's office, Oleksiy Arestovich, said in a video statement.

He was referring to a surprise Russian statement on Friday that it was time for Moscow to set as its "main goal" controlling Donbas, an eastern region already partly held by Russian proxies.

"This gives us hope in the area of Kyiv, Chernigiv, Sumy and Kharkiv regions, that we will drive the enemy out of here," Arestovich said, referring to north and eastern regions.

He also announced that Ukrainian forces were counter attacking against invading Russian troops in those areas, referring to small, tactical offensives.

Russian President Vladimir Putin ordered troops into Ukraine on February 24 with the aim of defending pro-Moscow separatists to and "demilitarise and de-nazify" the country.

The Russian announcement on Friday would amount to a sharp change of course with much limited goals that would not include an assault on the capital.

Moscow's month-long invasion on its pro-democracy neighbour has largely stalled with no major recent advances and Ukrainian forces even able to counterattack in places.