(CNN) -- Rescue workers in northern India are scrambling to save tens of thousands of people left stranded by devastating floods that have killed as many as 150 people in the region.
One government official described the flooding as a "Himalayan tsunami."
Triggered by unusually early and heavy monsoon rains, the floods have swept away buildings, roads and vehicles in the mountainous state of Uttarakhand, which borders Nepal and China. The neighboring state of Uttar Pradesh has also been hit.
"Our hearts go out to the families of those who have lost their lives and those who have suffered injury or loss of property in this huge tragedy," said Prime Minister Manmohan Singh, who carried out an aerial survey of the affected areas in Uttarakhand on Wednesday.
With bad weather hampering rescue efforts and some areas still under water, officials are struggling to gauge the scale of the disaster.
"Very heavy casualties are feared and I cannot give the exact number without a proper survey," said Uttarakhand Chief Minister Vijay Bahuguna, according to CNN's sister network CNN-IBN. He described the severe flooding as a "Himalayan tsunami."
Singh said Wednesday that estimates put the number of people killed in the floods at 102, but added that "it is feared that loss of lives could eventually be much higher."
A local official in Uttarakhand, Om Prakash, said that the death toll in the state had reached 150, but cautioned that he wasn't able to give an exact estimate since some villages were still inundated, CNN-IBN reported Thursday. More than 60,000 people remain stranded, the network said.
Flooding hits holy site
With Hindu shrines set amid its stunning scenery, Uttarakhand is often referred to as "the Land of Gods."
At the heart of the recent devastation is the town of Kedarnath, the home of a deeply revered Hindu temple that attracts many pilgrims. Images from the area have shown the centuries-old holy town, which sits in a deep valley, swamped with mud and rocks.
Rescue workers reached the town Wednesday and evacuated hundreds of people to safer areas, CNN-IBN reported, but thousands more remain stuck there. The temple is intact, but shops and other buildings surrounding it have been severely damaged, it said.
"The maximum damage has been in Kedarnath and its vicinity," Singh said.
The worst of the heavy rain came in the past few days in a region of India where the monsoon doesn't usually arrive for another month, according to Pedram Javaheri, a CNN International meteorologist.
"Some areas have seen more than twice their average monthly rainfall totals," he said. It's "the fastest India's ever seen the onset of the monsoon season."
The conditions have now improved somewhat, Javaheri said, predicting that the rain "should be scattered in nature for the next couple of days at least."
The weather has also brought chaos further south, in the Indian capital, New Delhi, where the Yamuna River has reached its highest level since 2010, according to CNN-IBN.
Flood waters have flowed out into parts of Delhi, inundating streets, shops and homes. Some water from the river has spilled out onto the city's Outer Ring Road, potentially disrupting traffic, CNN-IBN reported Thursday.
Authorities have relocated more than 5,000 people from affected areas, the network said, citing Delhi Chief Minister Sheila Dikshit as saying the situation is under control.
CNN's Harmeet Shah Singh contributed to this report.