Russian Foreign Minister Sergey Lavrov says he and his German counterpart have discussed resuming international talks on resolving the conflict in eastern Ukraine in light of escalating tensions.

Lavrov said after Monday's meeting with German Foreign Minister Frank-Walter Steinmeier that the situation is cause for "serious concerns" given Russia's recent contention that Ukraine sent "saboteurs" to carry out attacks in Crimea.

Moscow says two Russians were killed while preventing the incursions this month, while Ukraine denies they took place.

Steinmeier says Germany isn't clear what really happened and wants both Russia and Ukraine to investigate further.

Russia annexed Crimea from Ukraine in March 2014, and a conflict between Russia-backed separatists and Ukrainian forces flared up in eastern Ukraine weeks later.