A cease-fire in eastern Ukraine appeared to break down Tuesday when a rebel attack on a military helicopter killed nine people and a separate assault killed two soldiers, even as Russian President Vladimir Putin took steps to support the country’s tenuous peace process.

Putin asked parliament to revoke his legal authority to invade Ukraine, a move that Russian lawmakers approved Wednesday. He also said he supports the continuation of the cease-fire and direct negotiations between the Kiev government and pro-Russian separatists in eastern Ukraine.

But both sides traded accusations Tuesday that the other had violated the truce, and the downing of the helicopter near the rebel-held city of Slovyansk dashed hopes for peace a day after the warring parties held their first talks.

Ukrainian President Petro Poroshenko said in a statement after the helicopter downing that he may end the cease-fire early and that he had ordered military leaders to open fire in response to any attack. The truce is set to expire at 10 a.m. Friday.

Vladimir Seleznev, a Ukrainian military spokesman, said on his Facebook page that the Mi-8 helicopter was struck by a shoulder-fired missile shot from the village of Bylbasovka, just outside Slovyansk. The helicopter was delivering monitoring equipment, he said, and all nine people aboard were killed. Shelling at a checkpoint outside Slovyansk killed two soldiers, he said.

The deaths broke an uneasy quiet that had settled over the region after pro-Russian separatists agreed to the cease-fire Monday. The separatists are not a unified force and have at times battled internally. The leader of the Slovyansk separatists, a Russian citizen who goes by the name of Igor Strelkov, was not at the talks, where former president Leonid Kuchma represented Poroshenko.

Alexander Borodai, the main separatist interlocutor at the talks, said Tuesday on Russian state television that the discussions “turned out to be utter bluff. Kiev has not stopped the war.”

Putin, in Vienna to drum up support for a proposed natural gas pipeline to Europe that would bypass Ukraine, said he made the request to rescind his powers to invade the country because he and his government “want to create conditions for its peace process.” He called the fighting near Slovyansk “sad,” although he did not specifically address the helicopter attack.

Poroshenko, speaking earlier in the day, called Putin’s move the “first practical step of support for the peace plan.”

White House spokesman Josh Earnest said that the Obama administration found Putin’s move “welcome” but that it wants him to take “tangible actions” to calm the conflict.

Putin has been seeking to avoid significantly strengthened U.S. and European Union sanctions, which were threatened if Russia did not take steps to de-escalate the situation with Ukraine.

But Putin’s request to parliament appeared unlikely to change anything on the ground. U.S., E.U. and NATO officials have accused Russia of fomenting the insurrection in eastern Ukraine by channeling weapons, equipment and volunteer fighters across the porous border. Russia has denied the accusations, but if the Western officials are correct, the revocation of the authorization would do little to alter the situation.

“It’s only a symbolic gesture from him to support this peace process,” a senior Ukrainian security official said, speaking on the condition of anonymity because he was not authorized to talk to the news media. “I’d like to be optimistic, but I’m not,” he added, saying that he sees little reason for Putin to scale back what he said was a supply route of equipment to the rebels.

Russia’s upper house of parliament, the Federation Council, voted March 1 to authorize Putin to invade Ukraine if Russian interests were threatened there, soon after Russian-friendly Ukrainian President Viktor Yanukovych was ousted in the face of popular protests.

Weeks later, Russia annexed Ukraine’s autonomous Crimean Peninsula. And for much of March, April and May, according to U.S. and NATO officials, it had massed up to 40,000 troops along the border with eastern Ukraine, a destabilizing presence that fueled fear of a violent ground war.

A NATO spokeswoman said the defense alliance had not seen any change Tuesday in the posture of Russian forces along the border. NATO Secretary General Anders Fogh Rasmussen said last week that the Russian military had again begun a buildup along the border. A meeting of NATO foreign ministers that began Tuesday will focus on the Ukraine-Russia situation.

The United Nations estimates that 423 people were killed in eastern Ukraine between mid-April and June 20.