The Indian Navy plans to decommission its two remaining Soviet-built Foxtrot submarines, INS Vela and INS Vagli, by 2011.
India is operating INS Vela, commissioned in 1973, and INS Vagli, commissioned in 1974, while the Russian Navy decommissioned its last Foxtrots between 1995 and 2001, according to brahmand.com.
According to a senior Indian Navy official, INS Vela will be decommissioned this year and INS Vagli will retire in 2011.
The delay in the six-yearly refits made the navy's first four Foxtrot submarines, acquired from the Soviet Union and known as Kalvari Class submarines, not fit for operational use.
The Foxtrot Class diesel-electric patrol submarines can travel 16,000nm without refuelling and perform underwater operations continuously for four days, after which they have to change the air and charge batteries.
The Indian Navy has kept one of the decommissioned Foxtrot submarine in Visakhapatnam and converted it into a submarine museum.