A Ukrainian Su-25 fighter jet was flying close to Malaysia Airlines Flight MH17 before it crashed in eastern Ukraine, a Russian military official said on Monday.

The Ukrainian fighter jet flew within 3-5 km of the ill-fated Malaysian airliner before it was downed, Andrei Kartopolov, chief of the main operative department of the General Staff, told reporters.

Moscow would ask for explanation from Kiev, he added.

The Malaysian passenger jet strayed 14 km north from its planned route after passing Ukraine's eastern city of Donetsk, according to the official.

"The crew was attempting to return to the planned aerial corridor, but the flight was terminated at that moment," he said.

The Russian official also claimed that a group of Ukrainian Buk-M1 anti-aircraft batteries were redeployed near Donetsk on Thursday when Malaysia Airlines Flight MH17 crashed in the area, killing all 298 people on board.

"These surface-to-air systems are capable of hitting targets at a distance of up to 35 km at an altitude of 22 km. For what purpose and against whom were these missile systems deployed? As is known, the militia has no aviation," he said.