Ukraine's interior ministry says separatists in the country's east have detained a number of OSCE observers. Four Germans were among those captured, according to Germany's defense minister.
Kyiv said on Friday afternoon that "unknown persons" stopped the bus and that the occupants, which included observers from the Organization for Security and Cooperation in Europe (OSCE) and members of the Ukrainian armed forces, were taken to the city of Slovyansk.
"Near the entrance to Slovyansk, unknown persons stopped the bus with 13 passengers including seven OSCE representatives, five representatives of the armed forces of Ukraine and the driver of the vehicle," the ministry said in a statement.
"Negotiations are going on for their release," the statement said, adding the group was being held in an occupied security services building in the town, which pro-Russian separatists now control.
It said the rebels were demanding to speak with "the competent authorities of the Russian Federation."
German Defense Minister Ursula von der Leyen said four Germans were in the group - three members of the German armed forces, the Bundeswehr, and an interpreter.
Von der Leyen said contact had been made with the families of the four Germans, and that it was "important we now use all diplomatic channels so the team is released immediately and unharmed."
German Foreign Minister Frank-Walter Steinmeier spoke with his Russian counterpart Sergey Lavrov by phone on Friday, according to the news agency DPA. Steinmeier reportedly called for Moscow to help secure the release of the OSCE observers.
The main separatist leader and de facto mayor in Slovyansk, Vyacheslav Ponomaryov, has alleged that one of those detained was a military "spy" for the government in Kyiv.
Earlier on Friday, a Ukrainian military helicopter exploded while on the ground, near Slovyansk. The Mi-8 helicopter was hit by a rocket-propelled grenade, but authorities reported no injuries.
Tensions in recent days in Slovyansk have sparked clashes between the separatists and Ukrainian authorities. The Moscow supporters are calling for secession from Ukraine in favor of annexation by the Russian Federation.
jr/lw (Reuters, AFP)