MOSCOW (AFP) - A Russian rocket carrying a US telecommunications satellite plunged into the Pacific Ocean on Friday, only moments after being launched from a mobile sea platform.

"There was an accident during the Zenit rocket launch," a source at the Energia corporation that makes the Zenit-3SL rocket used to launch the Intelsat satellite said by telephone.

"The rocket fell into the Pacific Ocean. We have formed a commission to figure out the cause."

Energia chief Vitaly Lopota said the Russian rocket's engine appeared to fail less than a minute after the evening launch.

"We had an abnormal situation - the emergency shutdown of the first stage engine," Lopota told the state RIA Novosti news agency.

"It happened 50 seconds into the flight. We are now looking into what happened." The international Sea Launch consortium has used the former Pacific Ocean oil platform to perform commercial launches since 1999.

There had been only two complete failures out of the 34 missions conducted prior to Friday's launch.