)
Both the Ukraine government and pro-Russia separatists have cast doubt on a newly called ceasefire, following the downing of a military helicopter Tuesday, BBC reported.
Rebels shot down a Ukrainian helicopter carrying technicians Tuesday, killing all nine people on board.
Pro-Russia separatist leader Alexander Borodai said in his view there has "been no ceasefire".
Ukraine's President Petro Poroshenko warned he might end the truce due to "constant violation by rebels", the report said.
NATO chief Anders Fogh Rasmussen has accused Russia of failing to "respect its international commitments".
Rasmussen, in a statement, said Moscow was "using a new, different type of warfare against Ukraine", and he promised a "package of long-term support measures for Ukraine, including the creation of new trust funds".
Russia, however, denied claims by Ukraine and the West that it is encouraging and arming the separatists.
Insurgents had agreed Monday to observe a ceasefire, proposed by the Ukrainian government, until Friday, but Tuesday the Ukrainian military announced that separatists had shot down an Mi-8 helicopter outside the rebel-held city of Sloviansk, killing all nine people on board, the report said.
Poroshenko's office said gunmen had attacked government forces on 35 occasions since he ordered his troops to hold their fire.
