The Indian army brought in sniffer dogs, drones and heavy earth-moving equipment to search for scores missing a day after a deadly Himalayan flash flood.

At least four people were killed and around 100 are unaccounted for after a wall of muddy water and debris tore down a narrow mountain valley, smashing into the town of Dharali in Uttarakhand state.

"Additional army columns, along with army tracker dogs, drones, logistic drones, earthmoving equipment etc., have been moved... to hasten the efforts.

Military helicopters were working to bring in "essential supplies, medicines and (for the) evacuation of the marooned", the army said.

Uttarakhand State Chief Minister Pushkar Singh Dhami said the flood was caused by an intense "cloudburst" of rain, and that rescue teams had been deployed "on a war footing".

Videos broadcast on Indian media showed a terrifying surge of muddy water sweeping away multi-storey apartment blocks in the tourist region on Tuesday afternoon.

Several people could be seen running before being engulfed by the dark waves of debris that uprooted entire buildings.

Minister of State for Defence Sanjay Seth told the Press Trust of India (PTI) news agency late Tuesday that he had reports of "four deaths and around 100 people missing".