"The separation of the British satellite from the Russian Breeze M booster, which forms part of the Proton M rocket, took place at 11:46 Moscow time (07:46 GMT)," the Roscosmos spokesman said.
The Breeze M booster resumed service for the first time on Tuesday since it malfunctioned during the launch of a U.S. AMC-14 satellite in mid-March 2008.
I-4 satellites are among the largest and most sophisticated commercial communication satellites in the world, and are capable of delivering advanced voice and broadband data communications to mobile users.
Three I-4 satellites were built for Inmarsat by EADS Astrium. The I-4 F1 was launched in March 2005, while the I-4 F2 was launched in November 2005.
The Inmarsat 4F3 is owned by Britain's provider of mobile satellite communications services, Inmarsat plc.
The Russian-American joint venture International Launch Services (ILS) ILS provides satellite customers with a complete array of services and support and has exclusive rights to market the Proton, Russia's premier heavy-lift launch vehicle, to commercial satellite operators worldwide.
The launch of the Inmarsat-4 F3 will complete the I-4 constellation and support the global delivery of Inmarsat's latest services.