U.S.-led multinational military exercises began Monday in Ukraine after a day of deadly fighting between government forces and pro-Russian rebels in the restive east that has piled pressure on a shaky 10-day-old truce.

The decision to go ahead with the Rapid Trident exercise through Sept. 26 is seen as a sign of NATO’s commitment to support non-NATO member Ukraine while stopping well short of military intervention in the conflict. The crisis in Ukraine's vital industrial heartland in the east and Moscow's annexation of Crimea have sent ties between Russia and the West plunging to their lowest point since the Cold War.

As forces begin the exercise, the fragile cease-fire is an attempt to end a conflict that has cost more than 2,700 lives and sent at least half a million people fleeing battered towns and cities across the east. Ukraine, Russia, the separatists and the Organization for Security and Cooperation in Europe brokered the deal, which went into effect Sept. 5.

The United States is sending about 200 troops for Rapid Trident, the first such deployment since the pro-Moscow uprising erupted across eastern Ukraine in April. Soldiers from 15 nations are taking part in the exercise near the western city of Lviv, about 600 miles from the conflict in Donetsk.

U.S. President Barack Obama has rejected direct military involvement in the conflict but has unveiled tougher economic sanctions on Moscow that— together with similar EU measures — effectively lock Russia out of Western capital markets and hamstring its crucial oil industry. The punitive measures and an accompanying East-West trade war have left Russia's economy facing possible recession, and the ruble tumbled again Monday to a new low.

Rapid Trident will not involve live ammunition but will be a peacekeeping exercise with training in convoy operations, patrolling and methods of countering improvised explosive devices, or IEDs, said Pentagon spokesman Col. Steve Warren.

Taking place in the Yavoriv training center near Ukraine's border with Poland, it was initially scheduled for July but was pushed back because early planning was disrupted by the crisis.

Ukrainian Defense Minister Valeriy Geletey said Sunday that NATO member states were sending weapons to Ukraine, though this was previously denied.

A NATO official said he could neither confirm nor deny the claim "as any such delivery would be done on a bilateral basis.”

Meanwhile, local officials said six civilians died during heavy shelling around the rebel stronghold of Donetsk on Sunday, with Kiev accusing the separatists of jeopardizing the truce by intensifying attacks against government positions.

It is the highest civilian toll since the cease-fire signing, although a number of Ukrainian servicemen have also reportedly been killed over the past 10 days.

Ukrainian President Petro Poroshenko's office said late Sunday that German Chancellor Angela Merkel backed his plans to introduce legislation in parliament this week that would offer limited self-rule for the eastern regions that form the economic backbone of Ukraine — a key provision of the truce.

Sunday's fighting appeared to be heaviest near the Donetsk airport, where the Ukrainian military said it drove back an assault by insurgent fighters on Friday.

But the separatists accused Kiev's forces of failing to halt fire.

"From our side, nobody is shooting, but they are breaking the rules. Everybody in the world knows it," said a rebel commander defending a checkpoint near a village south of Donetsk.

Wire services