NATO on Monday urged Russia to use its clout with insurgents in eastern Ukraine to make a troubled truce stick, as the two sides held talks to defuse the worst tensions since the Cold War.

But NATO said gaps with Moscow remained wide as the alliance also raised "particular concern" over Russia's use of snap military exercises near eastern Europe that it says fuels instability.

"Allies called on Russia to use its considerable influence on the militants to meet their commitments in full," NATO chief Jens Stoltenberg said in a statement after the ambassador-level talks ended in Brussels.

Under the Minsk agreements in 2014 and 2015, Moscow agreed to a ceasefire in Ukraine and to halt support for separatist pro-Russian rebels that have carved out an enclave in the east of the country.

Provisions in the ceasefire deal call for the withdrawal of heavy weaponry from the regions of Donetsk and Lugansk.

"Allies raised particular concern over the excessive use of snap exercises. These are destabilising," Stoltenberg said.

He added that many participants in the talks called for updating the OSCE's Vienna Document on military exercises and activities.

Russian ambassador to NATO Alexander Grushko repeated accusations against Kiev, saying it was breaching the peace agreements.

"We pointed at the violations of the ceasefire by the Ukrainian military forces, their use of artillery systems forbidden by the Minsk agreements and the presence of heavy equipment in 'the security zone'," he said.

"We called on the... members to exert their influence on the Kiev authorities to encourage them to proceed from the de facto sabotage of the political process to real actions."

- Surge in tensions -

In August Russia conducted a large-scale snap drill, putting its troops on full combat readiness in military districts bordering Ukraine and the Baltic States.

Tensions between Russia and Ukraine surged over the summer after Moscow accused Kiev of attempting armed incursions into Crimea.

Ukraine and its Western allies have been locked in a bitter confrontation with Russia since Moscow seized the strategic region from Kiev in March 2014.

The third NATO Russia Council this year did not appear to bridge the divide -- Stoltenberg said "our meeting does not indicate a return to business as usual."

The NRC, which brings together ambassadors from the 28 NATO member countries and Russia, met regularly until the Ukraine crisis plunged relations with Moscow into the deep freeze in 2014.

US-led NATO has suspended all practical cooperation with Russia over its role in Ukraine but Stoltenberg has said political channels of communication have always remained open.

He says maintaining such contacts was crucial to avoiding any misunderstandings with Moscow at a time of increased tensions.

Stoltenberg gave no specific reason for convening the NRC on Monday but there has been growing speculation a meeting was on the cards, stoked by US president-elect Donald Trump's more conciliatory approach to Moscow.

Grushko meanwhile said the "situation in European security continues to degrade.

"The main negative factor is the ongoing strengthening of NATO's eastern flank, deployment of the US and Allied forces and equipment, reinforcement of military infrastructure along the Russian borders," he said.

Meanwhile, the European Union on Monday extended for another six months damaging economic sanctions against Russia over the Ukraine crisis.