Spokeswoman Christiane Wirtz said in a statement that Merkel "appealed to the president to use his influence" in resolving the situation.

The chancellor also reminded Putin of Russia's responsibility in the case because of its OSCE membership.

Eight military observers were taken hostage earlier this month and one has been released. The seven still being held include three German officers and a German interpreter.

The Kremlin said Putin stressed in the call that the main thing was for Ukraine to withdraw its troops from southeastern Ukraine, stop the violence there and quickly start a national dialogue on constitutional reform.

Both sides noted the potential of the OSCE for helping to resolve the crisis in Ukraine, the Russian statement said.

Merkel's spokeswoman said that the two leaders also spoke about the significance of the Ukrainian elections on May 25 "which are essential for the stability of the country."

Germany has decried Russia's annexation of Crimea as illegal.

(Agencies)

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