India showcased its military might during the Republic Day celebrations in New Delhi as US President Barack Obama looked on as guest of honour.

The 66th Republic Day, marking the day when the Indian constitution came into effect in 1950, is usually the occasion for India to parade its Soviet-style military strength to the world.

Amid unprecedented security measures in the Indian capital with about 50,000 personnel being deployed across the city, Obama became the first American president to be the chief guest at India's Republic Day events.

Incidentally, most of the missiles and machines that moved past during the display were of Russian origin, though some of the US equipment were also showcased.

The main attractions at the display were the arms developed locally, specifically the surface-to-air medium range missile, dubbed Akash, and the weapon-locating radar – both developed by India's Defence Research and Development Organisation.

The long-range maritime surveillance and anti-submarine P-8I aircraft, which was recently acquired by the Indian air force, and the MiG-29K fighter jets were also on display.

For the first time, three all-women contingents representing each of India's Army, Navy and Air Force marched during the parade at the Rajpath.

On the first leg of Obama's three-day visit, the two countries have already announced a key breakthrough in a civil nuclear deal between Washington and Delhi.

The nuclear deal has been kept on hold for nearly six years over concerns from both sides.

"We have forged a friendship, there is openness when we talk. The new partnership will not happen overnight. It will need patience but will remain a top foreign policy priority for my administration," said Obama during the joint press conference with Prime Minister Narendra Modi announcing the deal.

The two countries have also decided to boost annual bilateral trade to about five times the current value of about $100bn.