About 1,300 troops from 15 countries - including the U.S. and other NATO members - have begun a military exercise near Lviv in western Ukraine, according to BBC News.

The U.S. says the drills had been planned before the current crisis in eastern Ukraine, where government forces have been battling pro-Russian fighters. Clashes have continued in eastern Ukraine, particularly around the city of Donetsk, despite a ceasefire deal.

Over the weekend, Ukrainian Defense Minister Valery Heletey said Nato countries had begun arming his nation in the fight against the pro-Russian armed groups. He did not specify the type of weapons being delivered or name the countries involved.

Several NATO members have denied similar statements made in the past.

Officials from the alliance say they have no plans to send lethal assistance to non-NATO member Ukraine - but member states are free to do so on a bilateral basis.

Some 200 U.S. troops are taking part in the military exercise, codenamed Rapid Trident, near Lviv, on the Polish-Ukrainian border, some 1,000 km (600 miles) from the fighting in the east.

The exercise will bring together troops from several NATO member states and from former Soviet-bloc countries that are part of NATO's Partnership for Peace program.