Crisis in Ukraine

Pro-Russia separatists guard a checkpoint in Slovyansk, Ukraine, where seven delegates from the Organization for Security and Cooperation in Europe are among dozens of hostages held by the militants. (Roman Pilipey / European Pressphoto Agency / May 1, 2014)

German Chancellor Angela Merkel called Russian President Vladimir Putin on Thursday to urge him to use his influence with pro-Russia militants holding seven European military observers hostage in eastern Ukraine, official sources in Berlin and Moscow said.

But the Kremlin press service account of the phone call said Putin told Merkel that "the main thing" that needs to be done is for Ukraine's interim government to withdraw its forces from the southeast regions of the country.

Putin also said officials in Kiev needed to "stop the violence and immediately open a broad national dialogue" on constitutional changes that would transfer authority from the Ukrainian capital to the regions. The latter demand has been pressed repeatedly by the Kremlin in the month since its allied militants have occupied about a dozen towns and cities in eastern Ukraine, ostensibly to defend the interests of the region's Russian minority.

Masked and armed militants who seized the town of Slovyansk last month and declared the area part of the "People's Republic of Donetsk" detained a delegation of military observers from the Organization for Security and Cooperation in Europe on Friday as the group attempted to enter the town on a mission on behalf of the 57-nation group, which includes Ukraine and Russia.

The OSCE also has delegations of election monitors setting up observer operations for Ukraine's May 25 presidential election, as well as more than 100 members of a special monitoring mission dispatched after Russian troops occupied Ukraine's Crimea region in late February, which declared its independence after a hastily called referendum. Russia formally annexed Crimea last month, although the international community has condemned the move as an illegal.

The military monitors -- four Germans, a Swede, a Dane and a Pole -- were paraded by their captors last weekend in a news conference. The self-proclaimed mayor of Slovyansk, Vyacheslav Ponomaryov, has told journalists that the captives can be freed in exchange for separatists arrested by Ukrainian police during operations aimed at regaining control of the occupied areas. Five Ukrainian military officers were also in the OSCE delegation and were detained along with the Europeans, although the militants haven't disclosed their whereabouts or circumstances. The militants also hold Ukrainian and foreign journalists and Ukrainian activists pushing for unity in defiance of the separatists.

Kremlin officials, including Putin, have denied orchestrating the militancy in eastern Ukraine and feign inability to compel the gunmen to cease their disruptions.

Merkel "appealed to the president to use his influence" in resolving the standoff over the OSCE team, said Christiane Wirtz, a spokeswoman for the chancellor.

Russian Foreign Minister Sergei Lavrov, winding up a Latin America trip in Lima, Peru, on Wednesday, called for OSCE to oversee negotiations between the Kiev government and its "opponents" to resolve issues of concern to "our regions," referring to the Russian-speaking communities of southern and eastern Ukraine.

"We hope that our partners, our Western colleagues, will let the Ukrainians establish this dialogue without major impediments," Lavrov said, according to the Associated Press.

Lavrov and other top Kremlin officials have cast the confrontations roiling eastern Ukraine as the result of Western meddling and support for what were opposition politicians before the Feb. 21 ouster of Ukrainian President Viktor Yanukovich. Russian officials condemn the interim government as illegitimate and point to the spreading unrest in the east as evidence of Kiev's inability to effectively manage the country. The interim leaders in Kiev accuse the Kremlin of orchestrating the separatist turmoil to prevent or at least undermine a free and fair vote for a new Ukrainian president in little more than three weeks.

"Ukraine's ability to hold a credible election clearly is going to be tremendously difficult," said Olga Oliker, a senior international policy analyst at Rand Corp. whose expertise is in Russian foreign relations and military capabilities.

But Russia's membership in the OSCE and its tacit approval of the election monitoring mission suggests there may be sufficient observation of the presidential vote to bestow its legitimacy, Oliker said.

Opinion polls in the volatile eastern and southern regions of Ukraine suggest the population is largely opposed to Russian intervention or a breakup of Ukraine into pro-Russia and pro-Europe enclaves, Oliker said.

"The people of southern and eastern Ukraine do want legitimate government in Kiev and will come out and vote if they think they can do so safely and securely," she said, adding that the expected presence of OSCE and other international observers should have "a certain effect in deterring bad behavior."