GUWAHATI, India - Soldiers in motor boats rescued thousands of marooned people and helicopters air-dropped food as the number of people made homeless after some of the worst flooding in years in India's northeast rose to 3.5 million.

About 10 million people out of Assam's state 27 million population have been affected by flooding after rains in the past few days. More than 2,000 villages have been completely submerged.

The second spell of flooding in less than a month has also spread across parts of Bangladesh, forcing half a million from their homes and leaving thousands stranded.

"The situation is grim," the chief minister of tea- and oil-rich Assam state, Tarun Gogoi, told Reuters on Tuesday.

About 3 million people in Assam are living in temporary shelters, government buildings and schools, officials said.

Around 400,000 hectares (one million acres) of farmland have been flooded.

Since the annual monsoon rains began in June, about 50 people have been killed in Assam.

In the neighbouring state of Manipur, at least 55,000 people have been rendered homeless and are staying in more than 30 relief camps.

Road links to the tiny state of Sikkim, which borders China, remained disrupted as a large stretch of the main highway connecting the state with rest of the country was blocked by landslides.

The regional weather office in Guwahati - the main city in the country's northeast -- forecast more rains in the next 48 hours.

Prices of essential commodities have shot up across the region as landslides and flooding blocked highways at many places and trucks carrying food and medicines were stranded.

The chief minister of Manipur, Okram Ibobi Singh, ordered officials to release government food supplies for victims.