"According to our intelligence, Russian units are not withdrawing but repositioning. Russia is trying to regroup, resupply and reinforce its offensive in the Donbas region" in eastern Ukraine, Stoltenberg told a media conference.

"At the same time, Russia maintains pressure on Kyiv and other cities. So, we can expect additional offensive actions, bringing even more suffering."

The NATO assessment contradicted a pledge by Russian negotiators, made after talks in Turkey this week, to "radically" reduce Moscow's military activity in northern Ukraine, including near the capital Kyiv.

"We have heard the recent statements that Russia will scale down military operations around Kyiv and in northern Ukraine. But Russia has repeatedly lied about its intentions. So we can only judge Russia on its actions, not on its words," Stoltenberg said.

"It is obvious that we have seen little willingness from the Russian side to find a political solution," he said.

"We see continued shelling of cities and we see that Russia is re-positioning some of the troops, moving some of them around, most likely to reinforce their efforts in the Donbas region."

Stoltenberg added: "There is a close link between what is going on on the battlefield and what is going on around the negotiating table, and they do allow us to provide support Ukraine, to also strengthen their position at the negotiating table."