Two OSCE monitoring teams taken prisoner by separatist gunmen in eastern Ukraine are alive, the head of the European security body said Monday.

"We know where they are. They are alive and well," said Lamberto Zannier, secretary general of the Organization for Security and Cooperation in Europe.

U.S. President Barack Obama on Tuesday called on Russia to pressure separatists to stop attacking government forces in eastern Ukraine and to prevent the flow of fighters and weapons into the region.

Obama made the call in a press conference in Poland and also warned that further Russian action in Ukraine could lead to stepped-up economic sanctions.

India is making arrangements to evacuate close to 1,000 nationals, mostly students, from Ukraine's violence-hit Lugansk region, an official said Tuesday.  

"There are around 1,000 nationals, mostly medical students who are being evacuated," foreign ministry spokesperson Syed Akbaruddin told AFP. 

Ukraine's interior minister on Tuesday urged civilians across parts of the restive Donetsk region to stay indoors amid escalating fighting in the separatist east.

Interior Minister Arsen Avakov wrote on his Facebook page that residents in the rebel stronghold city of Lugansk and the neighboring towns of Kramatorsk and Krasnyi Lyman should not venture outside "in order to avoid risking their lives".

A Russian draft resolution calling for an immediate ceasefire in Ukraine and a humanitarian corridor met with criticism from the West and cool response at the Security Council Monday.

Moscow drafted the resolution at the start of its month-long presidency of the Council as Western powers want to enforce humanitarian corridors in Syria -- a prospect blocked by Russia.

NATO and Russia had a "very frank" exchange of views on the Ukraine crisis Monday but found no common ground in the first such meeting since Moscow annexed Crimea, officials said.

"I can say it was a very frank exchange of views," alliance spokeswoman Oana Lungescu said after a meeting of the NATO-Russia Council which groups the 28 member state ambassadors with their Russian counterpart.

The United States said Monday that Russia is continuing to support the pro-Russian insurgency in Ukraine, despite U.S. sanctions aimed at punishing it for its alleged interference in its neighbor.

"There is evidence that Russia continues to allow the free flow of weapons, funds, and fighters across its borders and President (Vladimir) Putin's next steps are still not clear," Treasury Secretary Jacob Lew said, in a speech in Washington.

Ukrainian forces killed five rebels on Monday while repelling an attack by 500 pro-Russian gunmen on a federal border guard camp in the strife-torn separatist east, Kiev officials said.

The border guard service said seven of its servicemen were wounded when "around 500 terrorists" attacked one of its units stationed outside the industrial city of Lugansk.

Russian President Vladimir Putin will hold face-to-face talks on the Ukraine crisis with British Prime Minister David Cameron, Downing Street said on Monday.

The two leaders will meet after they attend events to mark the 70th anniversary of the D-Day landings in Normandy, France, on Friday.

Russia will on Monday submit a draft resolution to the United Nations Security Council on creating a corridor to allow Ukrainians to escape areas affected by fighting, Russian Foreign Minister Sergei Lavrov said.

"Russia today plans to submit a draft resolution to the U.N. Security Council," Lavrov said at a televised news conference.