MOSCOW — An American member of the Organization for Security and Cooperation in Europe’s monitoring mission in eastern Ukraine died Sunday and two others were wounded when their vehicle was blown up by a mine in the separatist Luhansk region.

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

Austrian Foreign Minister Sebastian Kurz, who holds the rotating chairmanship of the OSCE, called for an investigation into the blast and said on Twitter that ‘‘those responsible will be held accountable.’’

The self-proclaimed security ministry for the Russia-backed separatist rebels in Luhansk said the mine had been laid by Ukrainian forces.

The rebels and the Ukrainian government have been fighting in eastern Ukraine since 2014 in a war that has killed more than 9,900 people.

The monitoring mission assesses compliance with the two-year-old Minsk peace deal that was to bring a cease-fire and heavy weapons pullback to the region. It also conducts work on human rights and civil society issues as well as mine-awareness programs.

In a separate development, Ukrainian investigators said they are preparing to ask a court to arrest an influential former lawmaker suspected of embezzlement, a second senior political figure to have been detained in the former Soviet republic in less than two months.

Mykola Martynenko, a top ally of former prime minister Arseny Yatsenyuk, was detained late Thursday in the capital, Kiev, after the National Anti-Corruption Bureau said it is preparing to file charges against him.

Associated Press