Russia's segment of the international network that monitors for signs of nuclear weapons tests will be completed this year, the defense ministry said on Friday.

The International Monitoring System was set up under the Comprehensive Nuclear Test Ban Treaty (CTBT) to detect seismic shocks or radioactivity resulting from any weapons test involving a nuclear explosion.

Russia says it will remain a part of this network despite withdrawing its ratification of the CTBT, a move that President Vladimir Putin signed into law on Nov. 2.

Russia's segment will be completed with the certification of its 32nd monitoring station, located on the Pacific island of Sakhalin, the ministry said.

It quoted a senior defense official as saying this was "indisputable proof of Russia's commitment to the non-proliferation of nuclear weapons and to strengthening nuclear stability in the world."

No country except North Korea has conducted a nuclear test since the start of the century, but some security analysts say Russia's withdrawal of its CTBT ratification could mark a step towards a resumption of testing, which could prompt other nuclear powers to follow suit.

Russia says it made the move in order to mirror the position of the United States, which has signed but never ratified the CTBT, and that it will not carry out a nuclear test unless Washington does.