MOSCOW - The shaky cease-fire in Ukraine was thrown into peril Tuesday when pro-Moscow separatists shot down a Ukrainian military helicopter, killing nine servicemen.
Ukrainian President Petro Poroshenko warned he may end the weeklong truce ahead of time. The deadly attack came a day after the rebels vowed to respect the cease-fire, which began last Friday.
Russian President Vladimir Putin, meanwhile, played the peacemaker, urging Ukraine to extend the truce and sit down for talks with the rebels. He also moved to rescind a parliamentary resolution authorizing him to use the Russian military in Ukraine.
Poroshenko declared the cease-fire as part of a plan to end two months of fighting between government troops and pro-Russian insurgents in the east. The violence, which erupted after the Kremlin's lightning annexation of Crimea in March, has left hundreds dead.
The cease-fire has been repeatedly broken by sporadic clashes, and it was violated again Tuesday when rebels used a shoulder-fired missile to down a helicopter in Slovyansk, a key flashpoint in the insurgency.
Poroshenko said in a statement that the insurgents had fired on Ukrainian positions 35 times since the cease-fire was announced, and he instructed Ukrainian soldiers to fire back "without hesitation" if attacked.