NEW DELHI - Half a million people in northeast India have been forced from their homes after flash floods inundated towns and villages, destroying property, crops and livestock, aid agencies said on Thursday.

Every year, torrential monsoon rains wreak havoc in Assam state, causing the mighty Brahmaputra river - one of Asia's largest - and its tributaries to breach embankments, displacing hundreds of thousands of people.

But aid workers say the situation this year is more alarming, with some 500,000 already displaced.

"The intensity of the rains is much higher than usual for this time of year," said Parvinder Singh, communications manager of international aid group ActionAid.

"This is just the beginning of the monsoons, yet embankments have been breached and we believe the situation is likely to get worse as the monsoon reaches its peak in the coming weeks."

Ten of Assam's 27 districts have been affected, including Majuli island - the world's largest inhabited river island where around 100,000 people are believed to be marooned.

According to aid agency ACT International, the flooding has isolated more than 500 villages in the four upper Assam districts of Lakimpur, Dhemaji, Jorhat and Naogaon, which are believed to be the worst affected.

Schools and colleges normally used as shelters during the monsoons have been inundated, forcing thousands of people to take refuge in makeshift shelters on raised embankments, with little food and water.

Tens of thousands of hectares of rice paddy crops have been destroyed and scores of livestock have died, say aid workers, adding that this raises health concerns as there are no proper strategies for disposing of carcasses.

The National Disaster Response Force are conducting search and rescue operations and state authorities have set up relief camps and are distributing rice and water purification sachets.