India's premiere defence research agency, the Indian Defence Research and Development Organisation (DRDO) began trials Thursday of an upgraded, Mk-II, version of the indigenously developed Arjun main battle tank (MBT). According to defence sources, the Arjun MBT will form the backbone of the Indian Army's armoured fighting units from 2014.

The Indian Indian Defence Research and Development Organisation (DRDO) received the green signal for developing the Mark-II version over a year ago after successful user trials of the Arjun Mk-I, which surprised sceptics even in the army.

The Arjun tank project has taken an inordinately long time to develop as continually shifting requirements from the army and other problems pushed it out of gear.

"The trials of the Arjun Mark-II tanks have begun at the Pokhran ranges in Rajasthan from today. The development programme is right on track and on schedule," senior defence ministry officials informed media.

"In 24 months from now, or in early 2014, the Arjun Mark-II tanks will be ready for production," senior DRDO officials had said in February this year.

The Arjun Mark-II is also expected to go through winter trials later this year. At present, there are 2456 T 72s, over 300 T 90s and 110 Arjun Mark I deployed across the country.