Russia will extend military drills in Belarus that were due to end on Sunday, meaning that Russian troops will not withdraw as previously announced, Belarusian Defense Minister Viktor Khrenin said on Sunday, amid the West's growing fears of an invasion of Ukraine.

Khrenin said the troops would remain in Belarus due to rising tensions in Ukraine's disputed Donbass region and "in connection with the increase in military activity near the external borders" of Russia and Belarus.

Incidents of shelling across the line dividing Ukrainian government forces and Russian-backed separatists in that region – which were sporadic in the past – increased sharply last week and continued on Sunday.

The decision to extend the drills beyond Sunday intensifies pressure on Ukraine, as Western leaders and the NATO defense alliance warn of an imminent full-scale invasion by Russia.

NATO says the 30,000 troops that Russia currently has in Belarus could form part of a planned incursion.

Russia has repeatedly denied plans to invade Ukrainian territory, despite the massing of around 150,000 troops along the country's borders, according to Western figures.

Speaking on broadcaster CNN's State of the Union show, United States Secretary of State Antony Blinken said that while all signs suggested Russia was on the brink of invading, the United States and its allies would use every diplomatic opportunity to dissuade the Kremlin.

Russian President Vladimir Putin and his French counterpart, Emmanuel Macron, discussed the need to step up the search for diplomatic solutions to the escalating crisis in eastern Ukraine in a phone call on Sunday, the Kremlin said in a statement.

Belarus did not say how long Russian troops in Belarus – estimated by NATO to number 30,000 – might now remain in the country, which borders Ukraine to the north. Belarus Defense Minister Viktor Khrenin said the focus of the extended exercises was "to ensure an adequate response and de-escalation of military preparations of ill-wishers near our common borders."

The Kremlin did not comment on the Belarus drills. Russia previously said the troops would return to permanent garrisons once the drills were over.

NATO says Russia could use the troops as part of an invasion force to attack Ukraine. Moscow denies any such intention.

Mykhailo Podolyak, an adviser to the Ukrainian president's chief of staff, told Reuters the extension of the Belarus exercises underlined that official promises from Moscow should not be taken as binding.

Russia and its allies say the West is whipping up tensions by sending NATO reinforcements to eastern Europe.

Kremlin spokesperson Dmitry Peskov said the repeated warnings by the West that Russia was about to invade were provocative and could have adverse consequences, without giving details.

Sanctions

Western countries are preparing sanctions they say would be wide-reaching against Russian companies and individuals in case of an invasion.

British Prime Minister Boris Johnson said in a BBC interview broadcast on Sunday that such sanctions could include restrictions on Russian businesses' access to the dollar and the pound. However, he acknowledged such threats may not deter Moscow, saying Putin may be "thinking illogically."

Ukrainian Foreign Minister Dmytro Kuleba said the West should impose some of the sanctions now, rather than waiting for an invasion.

Blinken said, however, that sanctions were a deterrent that should not be unleashed before an attack.

The focus of tensions in recent days has been on the swathe of eastern Ukraine that Russian-backed rebels seized in 2014, the same year Russia annexed Crimea from Ukraine. More than 14,000 people have been killed in the conflict in the east.

Ukraine's President Volodymyr Zelenskiy called on Sunday for an immediate ceasefire in the eastern part of the country.

On Sunday, a Reuters reporter heard explosions in the center of Donetsk city in the eastern Donbass region controlled by separatists. Heavy shelling was heard elsewhere in the region.

SMS messages sent to residents of Donetsk urged men to report for military duty.

More than 30,000 people from Donetsk and nearby Luhansk have crossed the Russian border in the past 24 hours, TASS news agency said, quoting authorities in Russia's Rostov region. The separatists began evacuating residents on Friday saying that Ukraine was planning to attack – which Kyiv denied.

Kyiv's Western allies are concerned Russia might use the escalation as a pretext for wider conflict.

Local military forces in one of the separatist areas, Luhansk, said on Sunday that two civilians had been killed and five buildings damaged in shelling by the Ukraine military. Russia's Investigative Committee will investigate the case, the RIA news agency quoted it as saying.

Two Ukrainian soldiers were reportedly killed with four more wounded on Saturday.

The International Committee of the Red Cross said water services had been disrupted for more than a million people in the region, and called on all sides to spare civilian infrastructure.

Ukraine's foreign minister Kuleba said Ukraine was not planning or carrying out any offensive operations.

Troop Build-up

The renewed fighting in eastern Ukraine follows a build-up over several weeks of Russia troops to the north, east and south of the country. The West estimates 150,000 or more Russian troops are currently near Ukraine's borders.

Russia, which has demanded NATO prevent Ukraine from ever joining the alliance, calls Western warnings it is planning to invade hysterical and dangerous.

However, it has warned of unspecified "military-technical" measures if its demands for NATO pullback from Eastern Europe are not met.

U.S. President Joe Biden was due to convene his top advisers later in the day to discuss the crisis. Biden said on Saturday he believed Russia could launch an attack "at any time," despite Kremlin assurances that some troops were returning to their permanent bases after military exercises.

A Russian diplomat at the United Nations said no-one should tell Russia where or when to conduct exercises.