New Delhi, Aug 10 (IANS): Defence Minister A.K. Antony Saturday congratulated defence scientists, personnel of the Indian Navy and other organisations for activation of the nuclear reactor on India's first nuclear submarine INS Arihant.

Sources said the nuclear reactor on Arihant was made critical Friday night and the submarine was on its own power now.

Antony termed it a very important milestone towards self-reliance in critical areas.

According to an official release, Antony said "tireless efforts" of scientists and other personnel had resulted in INS Arihant's nuclear reactor attaining criticality early Saturday morning.

He said the indigenous nuclear submarine would be "the pride of the Navy" when it joins the fleet.

Earlier, Prime Minister Manmohan Singh also lauded the scientists and defence personnel for activating the reactor on INS Arihant.

"I am delighted to learn that the nuclear propulsion reactor on board INS Arihant, India's first indigenous nuclear powered submarine, has now achieved criticality," he said.

INS Arihant has been undergoing trials at navy's submarine base in Visakhapatnam in Andhra Pradesh.