American tracking systems have registered the changes, a Mission Control expert said, adding that more precise information would be available by 9.50 Moscow time (6.50 GMT).
The orbital adjustment was needed to prepare the world's sole civilian space station for docking with the carrier rocket Soyuz TMA-8, which is to be launched from the Baikonur space station which Russia leases from the Central Asian republic of Kazakhstan, on March 30.
Soyuz will bring the next crew to the orbital station, with Brazil's first astronaut, who will spend a week at the ISS.
To widen the ISS orbit, four engines of Russia's cargo vehicle Progress M-54 currently docked to the ISS were started at 20.50 Moscow time (5.50 GMT) Wednesday, and worked for the planned 793 seconds.
Attempts to increase the station's orbit have not always been successful. For example, an operation to raise the ISS' average orbital altitude on October 19, 2005 failed when the cargo spaceship's engines stalled at the 170th second of the operation.
As a result, the station's orbit was only elevated by 450 meters instead of the planned 10 km. The stalling was attributed to an electronic engine control system failure.
Mission Control subsequently tested four of the spaceship's eight engines, before repeating the operation.
Orbital adjustments are routine operations needed to prepare the orbital station for receiving Progress cargo ships and manned Soyuz vehicles.
