The head of Russia's space program says foreign forces may be behind the recent failures of Russian spacecraft.

Roscosmos chief Vladimir Popovkin told the daily newspaper Izvestia that modern technology makes spacecraft vulnerable to foreign influence. But he said it is unclear why some Russian craft have malfunctioned while flying beyond the reach of the nation's tracking equipment.

He did not blame any other countries for Russia's space failures in recent months.

In November, Russia lost the Phobus-Grunt Mars probe, which failed to leave Earth's orbit after its launch. An unmanned launch attempt in August experienced a catastrophic failure.

Russia is the only nation transporting crewmembers to and from the International Space Station since the United States retired its space shuttle program in July.