DHAKA: A senior adviser to Russian President Vladimir Putin has lashed out at Ukraine's president ahead of the signing of a controversial EU deal.

Sergei Glazyev said Petro Poroshenko was a "Nazi" and his endorsement of the deal was "illegitimate".

Mr Poroshenko is expected to sign the full association agreement at the EU summit in Brussels later.

A shaky ceasefire in eastern Ukraine, where pro-Russian rebels are fighting government forces, is also due to end.

The pact - which would bind Ukraine more closely to the West both economically and politically - is at the heart of the crisis in the country and is strongly opposed by Russia.

Mr Poroshenko's predecessor Viktor Yanukovych refused to sign the deal and protests led to his overthrow, reports BBC.

After this Russia annexed Ukraine's Crimea region and pro-Russia separatists in eastern regions declared independence, claiming that extremists had taken power in Kiev.

In another development early on Friday, rebels released four international observers captured more than a month ago.

Alexander Borodai, head of the self-styled Donetsk People's Republic, said the members of the Vienna-based Organisation for the Security and Co-operation in Europe (OSCE) had been freed as a goodwill gesture.

"We don't expect anything in return - we freed them without any pre-conditions," he said.

The OSCE said it remains concerned about four other observers captured at about the same time.

BDST: 1355 HRS, JUNE 27, 2014