Russia has stopped using a sophisticated radar system in Azerbaijan after the two countries failed to reach an agreement to renew the lease.
The previous agreement on using the Gabala radar station expired on Sunday (December 9).
It was the last Russian base in the former Soviet republic, with an estimated 1,000 Russian and 500 Azerbaijani servicemen reportedly stationed there.
The Gabala radar station has a range of approximately 6,000 kilometers, covering regions south of Azerbaijan, including the Middle East.
Officials from the two countries have been negotiating an extension since 2011. Russian media report that Moscow's refusal to extend the lease agreement was due to Azerbaijan's insistence on increasingly higher rent.
Russia has been paying Azerbaijan $7 million per year for the use of the station, which was built in 1985. Reports say that Azerbaijan has demanded a huge rent increase.
Russia's Interfax news agency quoted an unnamed Russian diplomat as saying the issue is unlikely to affect Russian-Azeri relations negatively.