BRUSSELS (REUTERS) - Russia is likely to launch a new offensive in Ukraine's eastern Donbass region in the next few weeks, Nato Secretary-General Jens Stoltenberg said on Tuesday (April 5), adding that allies had time to help prepare the Ukrainian military.

Speaking a day before Nato foreign ministers gather in Brussels to discuss more financial, military and humanitarian support for Ukraine, Mr Stoltenberg said Russia was planning a "very concentrated" offensive.

"We now see a significant movement of (Russian) troops away from Kyiv to regroup, re-arm and re-supply and shift their focus to the east," Mr Stoltenberg told a news conference.

"In the coming weeks, we expect a further Russian push in eastern and southern Ukraine to try to take the entire Donbass and to create a land bridge to occupied Crimea," he said before Wednesday's meeting of Nato foreign ministers.

Mr Stoltenberg's comments appeared to confirm Moscow's announcement in late March that it was refocusing on "the complete liberation of the Donbass", an industrial region partly under Russian-backed separatist control since 2014.

Mr Stoltenberg said it would be a new, crucial phase of Russia's Feb 24 invasion, which the Kremlin calls a "special military operation".

"Repositioning of the Russian troops will take some time, some weeks," he said.

He said that: "In that window, it is extremely important that Nato allies provide support".

Foreign ministers on Wednesday and Thursday are set to discuss how to send more anti-tank weapons, ammunition and medical supplies to Ukraine, Mr Stoltenberg said.

Ukrainian Foreign Minister Dmytro Kuleba is expect to attend part of the two-day meeting in Brussels.