"The Foreign Ministry of Russia, being a depositary state, received on March 5 notification that North Korea has joined the 1966 space treaty," the source said.
The source said Pyongyang also told the Russian ministry that UN Secretary General Ban Ki-moon had been informed of the country's joining the 1974 Convention on Registration of Objects Launched into Outer Space.
North Korea's official news agency said earlier that the government has informed the International Maritime Organization and other related global bodies that the country will launch a satellite-carrying rocket between April 4 and 8.
A South Korean Foreign Ministry official said that despite Pyongyang's joining the agreements, the launch would be considered a breach of UN Security Council Resolution 1718, which prohibits the country from launching ballistic missiles.
The communist state announced plans last month to launch a satellite using a three-stage rocket from the newly constructed Musudan-ri launch pad on the country's northeast coast.
However, Seoul and Washington believe the real purpose of a satellite launch would be to test a long-range Taepodong-2 missile, which is thought to have a range of 6,700 kilometers (4,100 miles) and could possibly reach Alaska.
Pyongyang first tested a long-range missile in 1998, when it launched a Taepodong-1 over northern Japan and claimed that it carried a domestically-developed satellite.
In 2002, Pyongyang and Tokyo agreed to a moratorium on missile tests, but the secretive regime has continued research on ballistic missile technology.
In 2005 Pyongyang announced that it had nuclear weapons and in July 2006 test-launched a Taepodong-2 long-range missile and later staged an underground test of a nuclear device. On July 15, 2006, the UN Security Council passed Resolution 1695, which forbids North Korea from developing ballistic missiles.
The Taepodong-2 reportedly has a maximum range of 6,700 kilometers (4,190 miles), which would make it capable of hitting the U.S. states of Alaska and Hawaii, as well as South Korea and Japan.
Some analysts believe the impoverished country is not capable of developing a domestic space program, and that the planned rocket launch was simply an attempt to draw the attention of U.S. President Barack Obama's new administration to the issue of the stalled six-party talks on its controversial nuclear program.
The six-nation talks, involving North Korea, South Korea, Russia, Japan, China and the United States, were launched in 2003 after Pyongyang withdrew from the Nuclear Nonproliferation Treaty.