Nearly 1,000 people have been rescued after landslides in the hills of Wayanad district in India's Kerala state, authorities said on Wednesday, with at least 151 people dead and many still missing.

Heavy rain in one of India's most attractive tourist destinations collapsed hillsides early on Tuesday sending torrents of mud, water and tumbling boulders through tea and cardamom estates and small settlements. It was the worst disaster in the state since deadly floods in 2018.

At least 151 people died and 187 were still missing, the state chief minister's spokesman, P.M. Manoj, told Reuters by phone.

The Indian Army said it rescued 1,000 people and has begun the process to construct an alternate bridge after the main bridge linking the worst affected area of Mundakkai to the nearest town of Chooralmala was destroyed.

Near the site where the bridge was washed away, a land excavator was slowing removing trees and boulders from a mound of debris. Rescue workers in raincoats were making their way carefully through slush and rocks, under steady rain.

"We are quite sure there are multiple bodies here," said Hamsa T A, a fire and rescue worker, pointing to the debris. "There were many houses here, people living inside have been missing."

The landslides were mostly on the upper slopes of hills which then cascaded to the valley below, M R Ajith Kumar, a top state police officer, told Reuters.

"Focus right now is to search the entire uphill area for stranded people and recover as many bodies (as possible)," he said.

Nearly 350 of the 400 registered houses in the affected region have been damaged, Asianet TV reported, citing district officials.

After a day of extremely heavy rainfall that hampered rescue operations, the weather department expects some respite on Wednesday, although the area is likely to receive rain through the day.