MOSCOW, Feb 23 (Reuters) - A Russian Soyuz spacecraft blasted off on Friday on a mission to bring back to Earth a crew stranded on the International Space Station (ISS) by a leak in the cooling system of their original return capsule, Russian news agencies reported.

Tass news agency said the unmanned Soyuz MS-23 lifted off from Baikonur space centre in Kazakhstan and had been placed in orbit. It was due to dock with the ISS on Saturday at 0101 GMT.

Russian cosmonauts Sergey Prokopyev and Dmitry Petelin and U.S. astronaut Francisco Rubio had been due to end their mission in March. They were left stuck in space after the cooling system of their Soyuz MS-22 capsule started leaking two months ago.

Russian space agency Roscosmos said this week the trio would now return to Earth aboard Soyuz MS-23 in September. The damaged MS-22 spacecraft is now scheduled to land without a crew in March.

Both NASA and Roscosmos believe last year's leak on the MS-22 spacecraft was caused by a micrometeoroid - a tiny particle of space rock - hitting the capsule at high velocity.

A similar impact is also believed to have caused a separate leak this month on the cooling system of the Progress MS-21 cargo ship, taken out of orbit last week.

Tass said 430 kilogrammes (about 950 pounds) of cargo was sent aboard the replacement craft, including medical equipment, scientfic instruments, water, food and cleaning supplies. Tass quoted a Russian space official as saying the amount of food sent was three times the amount normally dispatched for such missions.

The leaks have prompted Roscosmos and NASA to rearrange their schedules and postpone planned space walks.