A land mine blew up a vehicle carrying an OSCE monitoring team in the separatist Luhansk region of eastern Ukraine on Sunday, killing an American observer and wounding two European members of the mission, officials reported.

The mission’s deputy head, Alexander Hug, said the member killed was from the U.S. and the two wounded are from Germany and the Czech Republic.

Austrian Foreign Minister Sebastian Kurz, who holds the rotating chairmanship of the Organization for Security and Cooperation in Europe, called for an investigation into the blast and said on Twitter that “those responsible will be held accountable.” Continue reading.