Days of relentless monsoon rains have killed at least 66 people in India, government officials said Wednesday, with dozens of foreign tourists stranded in the Himalayas after floods severed road connections.

Flooding and landslides are common and cause widespread devastation during India's treacherous monsoon season, but experts say climate change is increasing their frequency and severity.

Torrential downpours have washed away vehicles, demolished buildings and torn down bridges in Himachal Pradesh, the worst-affected state.

At least 33 people have lost their lives in the state -- popular for its picturesque Himalayan hill stations -- since Saturday, said Onkar Sharma, head of the state disaster agency.

Rescue teams were mobilised to assist 40 foreign travellers -- including 14 Russians and 12 Malaysians -- stranded at tourist destinations alongside several hundred Indian nationals, state police chief Satwant Atwal told AFP.

"Due to heavy snowfall and bad weather it has become very difficult to evacuate them," Chief Minister Sukhvinder Singh Sukhu said Wednesday on Twitter.

"We are exploring all possible options."

At least 12 people were killed in neighbouring Uttarakhand state, including nine on Tuesday when debris fell on their vehicles on a national highway, officials said.

A popular pilgrimage to the state's Kedarnath temple, home to a revered shrine of the Hindu deity Shiva, was suspended due to heavy rains.