RUDRAPRAYAG, India (Reuters) - Flash floods and landslides unleashed by early monsoon rains have killed at least 560 people in northern India and left tens of thousands missing, officials said on Saturday, with the death toll expected to rise significantly.

Houses and small apartment blocks on the banks of the Ganges, India’s longest river and sacred to Hindus, have toppled into the rushing, swollen waters and been swept away with cars and trucks.

“It has been a horrifying experience,” said Tulika Srivastava, a visitor from the northern Indian city of Lucknow, who has been stranded with her 80-year-old mother in the key pilgrimage town of Rudraprayag since last week.

Thousands of military servicemen are involved in rescue operations, with air force helicopters plucking survivors, many of them Hindu pilgrims and tourists, from the foothills of the Himalayas.

About 33,000 people had been rescued so far this week, the home ministry said. Railways were running special trains from the devastated areas to take people home.

“Whatever is humanly possible is being done,” Manish Tewari, the minister of information and broadcasting, told reporters.

The rains had eased on Saturday but more rain is expected early next week, complicating the task of rescuers. Rain will fall from Monday onwards in many places in the Himalayan foothills, said a weather official who sought anonymity.

Slideshow ( 6 images )

As many as 150,000 people were airlifted from the reach of the floods, said Dinesh Malasi, a rescue official at Dehradun, the state capital, with 60 helicopters pressed into the task.

Aid workers are struggling to negotiate roads blocked by landslides to reach the Kedarnath Valley, one of the worst affected areas, where thousands of pilgrims have been stranded. Some of those rescued by helicopter told charity officials in Dehradun they had seen bodies scattered everywhere.

Kedarnath, the site of a temple to a powerful Hindu deity, is 86 km from Rudraprayag in the hill state of Uttarakhand.

“The deaths will certainly rise,” said Madan Mohan Doval, an official of Sphere India, a group of non-government bodies working in the area that includes international charity Plan as well as the Indian Red Cross Society.

“People are in immediate need of basic aid such as dry food, clean drinking water, clothes, medicines, tarpaulin sheets for shelter and blankets,” Doval added.

Prime Minister Manmohan Singh has offered 200,000 rupees ($3,400) to the family of each of those who lost their lives and 50,000 rupees ($840) to the injured from his national relief fund. He also pledged money to people who have lost their homes.

Singh promised 10 billion rupees ($167 million) in disaster relief to Uttarakhand, home of the gods in Hindu mythology and the hardest-hit state.

The rains have not hit the summer sowing season in northern India so far, as the planting of rice, sugar, cotton and other agricultural produce is not yet in full swing. ($1=59 rupees)