A Russian military jet's landing gear malfunctioned as it touched down in the Czech Republic on Wednesday, injuring six people when it rolled off the runway, broke apart and caught fire, officials said. At least one man was in life-threatening condition.

The Russian-made An-30 plane had 23 people on board — 14 Russians and 9 Czechs, Czech military spokeswoman Jana Ruzickova said. The plane was on a mission sanctioned by the Open Sky treaty, which envisages surveillance flights over the territory of its participants, including NATO members, Russia and others.

Russian Defense Ministry spokesman Col. Igor Konashenkov said the plane's front landing gear collapsed as it was touching down at the Czech air force base in Caslav, some 20 miles east of Prague.

Czech military chief of general staff Gen. Vlastimil Picek blamed "a technical malfunction of the landing gear," but declined give further details.

Czech public television footage showed the plane broken in two and gutted by fire.

Ruzickova said five Russians and one Czech national suffered injuries, mostly burns. One Russian national who suffered burns to 20 percent of his body was in life threatening condition, said Hana Vranova, spokeswoman for Prague's Vinohrady hospital.

A Czech military committee is investigating the crash.