Germany calls for "air bridge" to supply besieged Aleppo

"In recent days there has been a spike in tensions around Crimea and that has anxious us", Steinmeier said at a news conference with his Russian counterpart Sergei Lavrov in Russia's fourth-largest city of Yekaterinburg.

But in more conciliatory comments, Lavrov said he did not think anyone was interested in cutting diplomatic ties between Russian Federation and Ukraine yet.

"Together with our German colleagues, and Frank-Walter personally, we will focus on striving to address issues, especially humanitarian ones, which were left over for us to deal with as a legacy following World War Two", he said.

Germany's foreign minister urged Russian Federation and Ukraine on Monday to reduce tensions over Crimea and stick to the troubled Minsk peace accords as a way of ending hostilities in eastern Ukraine. The saboteurs planned to target Crimea's critical infrastructure and vital facilities, the FSB said.

Lavrov said Moscow is prepared to provide "irrefutable" evidence of an alleged plan by Kyiv to launch sabotage attacks in Crimea, the Ukrainian region that Moscow annexed in 2014. The European Union said there was no independent confirmation of the killings. Russian Federation denies that its troops are in eastern Ukraine. He put the military on alert along the contact line with separatist forces and the frontier with the Black Sea territory.

They discussed the ongoing conflict in eastern Ukraine.

Russia's defense minister says Moscow and Washington are edging closer to an agreement that would help defuse the situation in the besieged Syrian city Aleppo.

Russian Federation has repeatedly accused Ukraine of not honouring its obligations under the peace deal.