Mariupol (Ukraine) (AFP) - "Will the Russians come today or tomorrow?" That is what the men defending the southeastern port of Mariupol were thinking as world leaders sat down Thursday to hammer out a ceasefire to end months of bloody conflict in Ukraine.

"Everyone can see what Putin says and what he does," said Dmytro Linkov, a commander in the pro-Kiev volunteer force, the Azov Battalion, on the barricades on the edge of the strategic city.

Earlier in the afternoon his men were attacked on the eastern approaches to Mariupol by what he claimed were regular Russian troops, wounding at least one of them. Four more are still missing, their equipment left abandoned as they retreated.

"Yesterday," he said, "we were going to have a ceasefire. And today, they (the Russians) move closer."

Now, even as Kiev prepares for talks with rebels on Friday to end the conflict that has killed some 2,600 people, there are fears that pro-Moscow rebels reinforced by what the West claims are regular Russian military units, could be preparing for a possible attack.

"Maybe they want to try to take Mariupol today," Linkov told AFP, standing in front of his checkpoint, next to a sign telling motorists they are leaving the city.

"They are getting closer, they are maybe 20 kilometres (12 miles) away," he said. "Two days ago, there were no more than ten (tanks), but now? Who knows?"

By nightfall, the rumble of artillery fire could be heard getting closer, with shells falling a few hundred metres from the checkpoint.

The West and Kiev say Russian troops are behind the lightning offensive that has seen pro-Moscow separatists seize back swathes of territory from government troops in recent weeks. The Kremlin flatly denied the charges.

Linkov said he is no doubt that the fighters he is facing are Russian.

They are so well-acquainted with the positions of armoured vehicles defending the city, he believes they must be working with aerial reconnaissance technology.

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"We can see that they are Russian, that they are not separatists, or terrorists. It is the regular Russian army, for sure," he said.

- 'Putin never stops' -

In the centre of Mariupol, hundreds of anxious residents marched to appeal for more help to fight back against what they called the "terrorists of Donbass" that are fighting to tie the eastern region to Moscow.

Some, frightened by rumours they had read on social media sites, were already considering whether to flee.

The Kiev-appointed governor of the Donetsk region, Sergiy Taruta, made a brief visit to the barricades in the afternoon, in an attempt to lift spirits.

Despite claims that Ukrainian forces have been in retreat, he said any movements were part of "the usual rotations".

"We have the means to take care of the whole Mariupol front," he said.

In the Welsh town of Newport, some 3,000 kilometres away, Kiev's leaders were also optimistic that they would soon be able to end the almost five-month long conflict with a deal on Friday.

President Petro Poroshenko voiced "careful optimism" about forging a ceasefire with pro-Moscow rebels at a meeting in Minsk brokered by the pan-European security body the OSCE.

But in Mariupol, the new frontline of the five-month conflict, there was scepticism that an end is in sight.

"I think they want to take Mariupol because this is the last big city in the region" still under Ukrainian control, said Linkov.

"Putin never stops. Not in Georgia, not in Ukraine. It's Russian politics," he said. "We must stop them."