The Russian Kilo Class attack submarine fist entered service in the early 1980s. It was designed by the Rubin Central Maritime Design Bureau in St. Petersburg. Subsequent developments have led to the current production versions, the Type 877EKM and most recently, the Type 636. The submarine was originally built at the Komsomolsk shipyard but is now constructed at the Admiralty Shipyard in St. Petersburg. 24 Kilo Class submarines are in service in the Russian Navy (most of older designs). They have also been exported to Iran, China, India, Poland, Romania and Algeria. China has two Type 636 submarines which are designed for anti-submarine (ASW) and anti-surface ship (ASuW) warfare as well as for general reconnaissance and patrol missions. The Type 636 submarine is considered to be one of the quietest diesel submarines in the world. It is said to be capable of detecting an enemy submarine at a range three to four times greater than it can be detected itself.