NEW DELHI (AFP) - India stepped up its search for the missing Malaysia Airlines plane carrying 239 people, deploying three ships and three aircraft to the remote Andaman and Nicobar Islands, a navy source said.

The defence ministry ordered deployment of the vessels and planes to scour an area east of the islands in the Andaman Sea which are closer to Myanmar and Malaysia than India, a senior navy official said.

"India has formally joined the search operations this afternoon for the missing Malaysian airliner by sending three ships," the official said in New Delhi, adding that India was coordinating with Malaysia's navy.

Malaysia is no closer to finding the plane that lost radar contact on Saturday, en route from Kuala Lumpur to Beijing, amid confusion and contradictions about what could have happened to it.

The search for the plane now encompasses both sides of peninsular Malaysia, over an area of nearly 27,000 nautical miles (more than 90,000 square kilometres) - roughly the size of Portugal - and involves the navies and air forces of multiple nations.

The Indian operation "is being conducted from the naval headquarters in New Delhi. Being a maritime search and rescue operation, the government... has asked the Indian navy to lead and conduct the operations," the navy official said, adding that two Dornier aircraft and one P-8I maritime surveillance plane have also been deployed.

He said the INS Saryu, INS Kumbhir and ICG Kanaklata Barua were expected to reach the search area some 111 nautical kilometres (60 miles) east of Campbell Bay, on one of the southern islands, by late Thursday.

The Andaman and Nicobar islands are Indian territory, although they are at least 1,000 kilometres (600 miles) from the mainland.

India's coastguard joined the aerial search on Wednesday, deploying one aircraft also to the east of the Andamans.