The North Korean Army has deployed about 900 new tanks equipped with improved armament in the last seven years to modernize its aging vehicles, a South Korean military source said Wednesday.

The new tanks, known as the "Chonma-ho 5" (sky horse) and the "Songun-ho" (military first), are equipped with an advanced fire control system and turret guns, an upgrade compared to the Pokpung-ho (storm) tank, which was first revealed in October 2010 during a military parade. 

The Chonma-ho 5 is the latest variant of North Korea's main battle tank, the Chonma, which was built based on the Soviet T-62 tank. 

"The North Korean military has deployed 900 new tanks from 2005 until last year," the source said, asking for anonymity as the information is classified. "The number is more than double of South Korean tanks deployed during the same period."

The Songun is believed to have been named after the military-first policy heralded by former North Korean leader Kim Jong-il as a guideline for ruling the impoverished, communist country. The vision has been upheld by his young son, Jong-un, who is pursuing missile and nuclear weapons programs despite international warnings.

About 100 Songun tanks were spotted recently and South Korea's Joint Chiefs of Staff acknowledged that North Korean ground forces have garrisoned the new tanks, the source said.

The new tanks are expected to become a considerable threat to South Korean armored units as they have a longer range and a maximum speed of 70 km/h on paved roads.

Beginning in the late 1970s, Pyongyang started to produce a modified version of the 115mm-gunned T-62 tank, and since then it is believed to have made considerable modifications to the basic Soviet and Chinese designs.

According to South Korea's 2012 defense white paper, the North has stockpiled about 4,200 tanks.

The South Korean Army operates about 2,400 tanks, the defense paper said, many of which will be replaced by the K2 main battle tank and the modified K1A1 tank. Rolled out in 2007, the K2 is an amphibious tank armed with a locally developed 120mm/55-caliber stabilized smoothbore gun. (Yonhap News)