At least 41 people have died and more than a dozen are missing after landslides and flash floods triggered by several days of heavy rain hit northern India.

Officials in the Himalayan state of Uttarakhand said 35 people were killed in fresh landslides today after six died in similar incidents yesterday.

At least 30 of them were killed in seven separate incidents in the worst-affected Nainital region early today, after cloudbursts - an ultra-intense deluge of rain - triggered a series of landslides and destroyed several structures.

"So far 30 people have been confirmed dead, while many people are still missing," Nainital senior civil officer Ashok Kumar Joshi said.

He added that several remote areas in the hilly region witnessed widespread damage in the intense rainfall.

Five of the dead were from a single family whose house was buried by a massive landslide, according to another local civil officer Pradeep Jain.

Another landslide in the northern Almora district killed five people after huge rocks and a wall of mud demolished and engulfed their home.

At least six others were killed yesterday in two remote districts of the state.

The Indian Meteorological Department extended and widened its weather alert, predicting "heavy" to "very heavy" rainfall in the region over the next two days.

The weather office said several areas were drenched by more than 400 millimetres of rainfall yesterday, causing landslides and flooding.

Authorities ordered the closure of schools and banned all religious and tourist activities in the state.

Television footage and social media videos showed residents wading through knee-deep water near Nainital lake, a tourist hotspot, and the Ganges bursting its banks in Rishikesh.

More than 100 tourists were stuck inside a resort in Ramgarh after the overflowing Kosi river deluged several areas.

Landslides are a regular danger in India's Himalayan north, but experts say they are becoming more common as rains become increasingly erratic and glaciers melt.

Experts also blame construction work on hydroelectric dams and deforestation.

In February, a ferocious flash flood hurtled down a remote valley in Uttarakhand, killing around 200 people. At least 5,700 people perished there in 2013.

Forecasters have also warned of more downpours in the coming days in the southern state of Kerala where floods have already killed at least 27 people since Friday.

Many dams in the state were nearing the danger mark and authorities were evacuating thousands to safer locations as major rivers overflowed.

India's weather office said heavy rains will again lash the state in the next two days after a brief reprieve today.