Ukraine army helicopter 'shot down' despite ceasefire

Before Tuesday, the rebels had shot down at least two Ukrainian army helicopters and a plane

The Ukrainian military says one of its helicopters has been shot down by pro-Russian rebels in the east, killing all nine people on board.

It says the Mi-8 helicopter, used for transporting military cargo, was hit by a rocket shortly after take-off outside the rebel-held city of Sloviansk.

It comes a day after the rebels vowed to observe a ceasefire until Friday, in response to a government peace plan.

But Russia's president warned that the week-long truce was not enough.

Vladimir Putin said it should be extended to try to hold "substantive talks" between the Ukrainian government and the separatists.

The rebels have not commented publicly on the Ukrainian military's claims.

Before Tuesday, the rebels - who continue to hold towns in the regions of Donetsk and Luhansk - had shot down at least two Ukrainian army helicopters and a plane.

The rebels say they will not disarm until government troops have left eastern Ukraine

Analysis: David Stern, BBC News, Kiev

One would suspect that the Ukrainian government's truce in the east is now a dead letter. President Petro Poroshenko's plans to respond to the attack are still unclear, but public outrage alone would seem to demand some sort of military retaliation.

And if the Ukrainian government uses force, then very likely the Ukrainian insurgents and their Russian comrades-in-arms will answer in kind. An escalation seems inevitable.

At this point, it is close to impossible to determine why the militants decided to carry out such a provocative act, just one day after they declared a ceasefire. Maybe this was some rogue element. Maybe the insurgents were never serious. Maybe Moscow told them to do it.

Whatever the reason, the hopes of just 24 hours ago, that Ukraine's east could finally see peace, if only temporarily, ring especially hollow.

'Russian world'

Earlier in the day, President Putin asked the Russian parliament to revoke the right of military intervention in Ukraine.

Former Ukrainian President Leonid Kuchma (second left), OSCE Ambassador Heidi Tagliavini (centre) and Russian Ambassador to Ukraine Mikhail Zurabov joined the talks with the separatists

President Putin stressed that Moscow would continue to protect ethnic Russians in Ukraine

Mr Putin was met by protesters in Vienna, who demanded an end to Russia's intervention in Ukraine

The move was aimed at "normalising the situation" in the eastern regions of Ukraine, Mr Putin's press secretary said.

The parliament authorised Mr Putin to use force in Ukraine on 1 March.

Ukrainian President Petro Poroshenko said Mr Putin's latest move was a "first practical step" towards settling the crisis in the east. It came after Russia had officially supported Ukraine's peace plan, which included the week-long ceasefire.

But speaking later during a visit to Austria, Mr Putin stressed that revoking the right on using force did not mean that Russia would stop protecting "ethnic Russians in Ukraine... who consider themselves part of the broad Russian world".

Since March, Moscow has annexed Ukraine's southern Crimea peninsula - a move condemned by Ukraine and Western leaders.

The takeover achieved with the help of troops without insignia. Despite initial denials, Mr Putin later admitted that they were Russian armed forces.

However, Russia denies accusations by Ukraine that Russian troops are helping and arming the separatists in eastern Ukraine.