Merkel calls for direct talks between Russia, Ukraine

German Chancellor Angela Merkel has underscored the urgency of holding direct talks between Russia and Ukraine, a German government spokesperson said.

She called for it during a phone conversation with Russian President Vladimir Putin Sunday.

The two leaders have talked about the tense security situation in Ukraine without prejudice to their different views on the referendum in Ukraine's Crimea and the issue of territorial integrity and sovereignty of Ukraine, spokesperson Steffen Seibert said in a statement.

The German chancellor said the existing presence of the Organisation for Security and Cooperation in Europe (OSCE) in Ukraine should be quickly expanded and a larger number of observers be sent to conflict areas, in particular in eastern Ukraine.

The chancellor also stressed that it is urgent and necessary for the governments of Russia and Ukraine to hold direct talks to solve problems.

Crimea is holding a referendum Sunday on its future status. The vote was described by some western countries as illegal.

Putin told Merkel during the phone talk that the ongoing Crimea referendum does not breach international law, the Kremlin reported on its website.

"Putin said the Crimean population's vote is proceeding in full compliance with international law, in particular with Article 1 of the UN Charter that stipulates the principle of equality and self-determination of peoples," the Kremlin website said.

"Russia will respect the choice of Crimean residents," Putin said, adding that he was concerned about the aggravation of the situation in eastern and southeastern regions of Ukraine, according to the Kremlin webiste.