(QHA) -

Ukrainian President Petro Poroshenko has demanded the immediate release of all Ukrainian prisoners captured during the conflict with pro-Russian rebels in eastern Ukraine, inlcuding pilot Nadia Savchenko, who has been on a hunger strike in a Russian jail since December 15. 

Poroshenko, speaking on January 21 at the World Economic Forum in Davos, Switzerland, said the prisoners were "hostages who are illegally held in the occupied territories and in Russian prisons." 

Earlier on January 21, the president of the Parliamentary Assembly of the Council of Europe (PACE) asked the Kremlin-allied speaker of Russia's lower house of parliament to help secure Savchenko's urgent release.

PACE President Anne Brasseur also expressed concern over the health of Savchenko. Brasseur made the appeal in a letter to State Duma speaker Sergei Naryshkin, the assembly said in a statement on January 21.

It said Savchenko, who was elected to the Ukranian parliament in October 2014, should be released to enable her to attend the opening of a PACE session in Strasbourg on January 26.

Russia has charged Savchenko with involvement in the deaths of two Russian journalists killed in the conflict in eastern Ukraine.