MOSCOW (AP) -- Russia launched three navigation satellites into space on Wednesday on a Proton-K booster rocket that blasted off from the Baikonur Cosmodrome in Kazakhstan, the Space Forces said.

The satellites are to become part of the GLONASS satellite navigation system of the Russian military.

The system, developed during the 1970s, originally had 24 satellites but their number has dwindled. The three satellites launched Wednesday will bring the system strength up to 12, according to the ITAR-Tass news agency, which added that the system needs 15-18 satellites to operate normally.

Sergei Derevyashkin, a Space Forces spokesman, said the heavy booster had shot into space at 2:38 a.m. EST (0738 GMT). The satellites were set to enter their targeted orbit about four hours later.

GLONASS, a Russian acronym for Global Navigation Satellite System, was developed by the Russian military to enable ships, planes and ground troops to pinpoint their position anywhere on earth to within 50 feet (15 meters).

Like the United States' satellite network, called the Global Positioning System (GPS), the Russian network can be used by civilians who have the proper equipment. But the location devices are not yet widely available in Russia.