Ammon News - AMMONNEWS - Rebel fighters have shot down a Ukrainian military helicopter carrying technicians who had been installing equipment to monitor a peace plan in Ukraine's east, killing all nine people on board.

The incident took place just hours after pro-Russian separatists on Monday night announced a ceasefire until June 27 to match a week-long truce by government forces which has been ordered by Ukraine's President Petro Poroshenko.

The technicians had been returning from setting up specialised equipment on Tuesday when their Mi-8 cargo helicopter was struck by a rebel missile near Slovyansk in eastern Ukraine, Vladyslav Seleznyov, government forces spokesman, said.

"There were nine people on board. According to preliminary information ... all those on board were killed," Seleznyov said on his Facebook page. The dead included a three-man crew.

"The [rebel] fighters, having fired the rocket, hid in the nearby village of Bylbasovka," he said.

It was the second time a helicopter has been brought down by rebel fire from Slovyansk, a separatist stronghold. On May 30, separatists downed a military helicopter killing 14 servicemen, including one general.

Dmytro Tymchuk, a military analyst with sources in the armed forces, said the helicopter had been brought down by a missile fired from a shoulder-held launcher.

Fresh pressure feared

The truce announcement by separatist leaders had raised the first real prospect of an end to hostilities since the conflict erupted in the largely Russian-speaking east in April.

But the helicopter incident seemed certain to put the ceasefire on both sides under fresh pressure.

Al Jazeera's Paul Brennan, reporting from Donetsk, said while the ceasefire remained in name, the problem was that it was not being properly observed on the ground.

"If there's nobody independent who can actually monitor the ceasefire that's taking place ... it's very difficult to have a ceasefire that actually means anything," Brennan said.

Elsewhere, a rebel spokesman in Donetsk said a shootout broke out near the city's airport, which is under Ukrainian control.

Rebels opened fire on two Ukrainian armoured personnel carriers leaving the grounds of the airport, according to a witness.

Earlier on Tuesday, Poroshenko had said the separatists had violated their own ceasefire with overnight attacks on military posts and checkpoints which killed one government soldier and wounded seven others.

His plan offers a safety "corridor" back to Russia for pro-Russian fighters who lay down their arms. It has secured the backing of Western governments and qualified support from Russian President Vladimir Putin.

Some of the rebels said they would adhere to the ceasefire after talks between separatist leaders and a "contact" group of officials who included a former Ukrainian president, Russia's envoy to Kiev and a high-ranking representative from the Organisation for Security and Co-operation in Europe (OSCE).

But in Slovyansk, near where the helicopter was brought down, separatists appeared to be dissociating themselves from the ceasefire agreement.

"Talks with them [the Kiev government] are possible only from a position of force and no other way. We should not trust a single letter," said Igor Strelkov, the rebel commander in Slovyansk, as quoted on the Facebook page of Pavel Gubarev, the self-styled governor of the "Donetsk People's Republic".

"They [Ukrainian troops] are trying to quickly and calmly take and reinforce new positions under the cover of the
ceasefire treaty."

Putin revokes intervention right

Meanwhile, Vladimir Putin, the Russian president, asked Russia's upper house on Tuesday to revoke the right it had
granted him to order a military intervention in Ukraine in defence of Russian-speakers there.

Ukrainian President Petro Poroshenko called Putin's move a "first practical step" following the Russian president's statement of support last weekend for Poroshenko's peace plan.

The United States also welcomed Putin's move but said that it wanted to see "tangible actions" from Russia to de-escalate the crisis.

*Agencies