Russia on Tuesday launched three satellites to complement its space navigation system, officials said.

The satellites were sent into orbit on a Proton-M rocket that blasted off successfully from the Baikonur launchpad in Kazakhstan, said Russia's Federal Space Agency spokesman Alexander Vorobyov.

They are to join Russia's Global Navigation Satellite System, or GLONASS — the equivalent of the U.S. Global Positioning System, or GPS.

The system, which serves both military and civilian purposes, was developed during Soviet times and is supposed to have 24 satellites. Their number dwindled after the 1991 Soviet collapse, but the government has earmarked funds to revive the system to its full strength thanks to Russia's windfall oil revenues.

Russia's First Deputy Prime Minister Sergei Ivanov said that Tuesday's launch would bring the GLONASS satellite fleet to 18 — the number necessary to provide navigation services over the entire Russian territory. He said Monday that the system would be available worldwide by 2010, for which it would need to have 24 satellites.