New Delhi (PTI): More than 20 people were killed, homes washed away and hundreds left stranded as torrential rains triggered landslides and caused rivers to swell in parts of north India. With many missing, rescuers raced against time, scrambling through uprooted trees and collapsed buildings to look for survivors.

Down south, the death toll in the devastating landslides in Kerala's Wayanad district climbed to 177 on Thursday, with authorities saying that it could increase further as rescue operations are still under way.

Heavy overnight rain in Uttarakhand claimed 12 lives, flattened homes and left several areas submerged.

Haridwar district reported six deaths, Tehri three, Dehradun two and Chamoli one. Two persons, one each in Haldwani and Chamoli, are missing, the Disaster Control Room said.

Water entered many homes in Dehradun and roads at various places in the city were waterlogged. Many colonies and markets in Bhupatwala, Haridwar, Naya Haridwar, Kankhal and Jwalapur were also flooded.

Three members of a family -- Bhanu Prasad (50), his wife Neelam Devi (45) and their son Vipin (28) -- were killed in a landslide triggered by a cloudburst at Jakhanyali village in Tehri, the officials said.

They said 450 pilgrims bound for Kedarnath were stranded beyond Bhimbali along the Gaurikund-Kedarnath trek route after 20-25 metres of the stretch was washed away by heavy rain.

The pilgrims stranded on the trek route to Kedarnath are being brought to an emergency helipad, Chief Minister Pushkar Singh Dhami said in a post on Facebook.

Dhami visited the disaster management centre in Dehradun on Thursday morning to review the situation across the state and asked officials to remain alert.

In Rudraprayag district, the Mandakini and Alaknanda rivers were flowing close to the danger mark.

Teams of National Disaster Response Force (NDRF), State Disaster Response Force (SDRF) and local administration have been deployed in the affected areas of the state, the officials said.

Neighbouring Himachal Pradesh also reeled under monsoon fury as multiple cloudburst incidents killed five people and left about 50 missing. Homes, roads and bridges were swept away by torrents of mud and water.

The state emergency operation centre said the cloudbursts occurred in Nirmand, Sainj and Malana areas in Kullu district, Padhar in Mandi and Rampur district in Shimla district.

The Manali-Chandigarh National Highway has been damaged at several places due to landslides, an official said.

According to officials, teams of NDRF, Indo-Tibetan Border Police (ITBP), police and home guards had launched rescue operations and drones were being used to locate missing persons.

A breach was also reported in Malana Dam in Kullu but the situation is under control, the officials said.

Some people are stuck in the Malana I hydropower project. They are in underground buildings and safe and NDRF and home guard teams are trying to rescue them, Deputy Commissioner, Kullu, Torul S Raveesh, told PTI.

Union Home Minister Amit Shah spoke to Himachal Pradesh Chief Minister Sukhvinder Singh Sukhu and took stock of the situation. Shah assured him of all help from the Centre.

Heavy rains have lashed parts of Himachal Pradesh since Wednesday evening. Palampur received the highest rainfall in the state at 212 mm, according to the meteorological department.

Chauri received 203 mm of rainfall, Dharamshala 183.2 mm, Jogindernagar 161 mm, Kangra 150 mm, Sujanpur Tira 142 mm, Baijnath 135 mm, Shimla 64.6 mm, Sainj 61 mm and Bilaspur 56 mm.

The Shimla meteorological centre has issued a 'red alert' for heavy to extremely heavy rain along with thunderstorms and lightning at isolated places in the state's Kangra, Kullu and Mandi districts on Thursday. It also warned of landslides, mudslides and land sinking.

Rains claimed three lives in Delhi.

While a man died when a building collapsed in north Delhi's Sabzi Mandi area on Wednesday night, a woman and her three-year-old son drowned in a drain on a waterlogged road near the Khoda Colony area, officials said.

Three people were also injured in wall collapse incidents in Defence Colony and Shastri Nagar areas, they said.

Heavy rain unleashed chaos in Delhi on Wednesday evening, inundating large parts of the city, while key stretches were choked with unending traffic.

Till 7 am, Delhi Police had received 2,945 calls of traffic jams, 127 calls of waterlogging, 27 calls about building collapses and 50 calls about fallen trees, the officials said.

In Rajasthan's Jaipur, three members of a family drowned as rainwater entered the basement of their house in Vishwakarma area on Thursday morning, officials said.

The bodies of Kamal Shah (23), Pooja Saini (19) and her niece Purvi Saini were recovered by the SDRF during an hours-long rescue operation, they said.

According to the Jaipur Meteorological Department, Karauli, Sawaimadhopur, Alwar, Churu, Bharatpur, Tonk, Sikar, Hanumangarh, Dholpur, Nagaur and Jhunjhunu received heavy to very heavy rain in the past 24 hours ending at 8.30 am on Thursday.

Jaipur received the highest rainfall of 173 mm during this period, the weather office said.

In Karnataka, a 56-year-old woman died after her house partially collapsed at Nellikaru village in Udupi district due to heavy to very heavy rain, officials said.

The Phalguni river in Dakshina Kannada and the Shambhavi river in Udupi district are in spate following torrential rains over the past two days, they said.

Two days after landslides triggered by torrential rains upended lives in Kerala's Wayanad district, rescuers continued to dig through mud and debris in search of survivors.

The death toll climbed to 177 on Thursday with the district administration saying it may increase further.

More than 200 people were injured in the landslides that hit the hilly district in the early hours of Tuesday while many were fast asleep.

The India Meteorological Department has warned of heavy rain in West Bengal and Odisha over the next two days.