The ashes of assassinated prime minister Indira Gandhi were scattered today over the snowy Himalayan mountain range that she loved and revered throughout her life, bringing to an end 12 days of state mourning by a stunned nation.

Rajiv Gandhi, her son and successor to the leadership of India, dropped the ashes from an Indian Air Force transport plane flying at 25,000 feet between Gangotri, the source of the holy Ganges River, to Amarnath, a traditional shrine for Hindu pilgrims. The route stretched from Uttar Pradesh, the state in which she was born, to the state of Jammu and Kashmir, whence her Nehru family ancestors migrated centuries ago.

As a child, Indira Gandhi frequently had visited and ridden horseback through the majestic Himalayan foothills with her father, Jawaharlal Nehru, India's first prime minister, and she stipulated before her death that her remains be strewn there.

Gandhi, who was shot to death in the garden of her New Delhi residence on Oct. 31 by two Sikh security guards, was cremated Nov. 3 by the banks of the Yamuna River here.

Rajiv Gandhi, his wife, Sonia, their two children, Rahul and Priyanka, and a few close relatives took off at 8:15 a.m. from Hindon Air Base near here in a Soviet-built, propeller-driven AN12 transport plane carrying the ashes that had been returned to New Delhi from the capitals of 22 Indian states and nine union territories after public viewing by millions of mourners.

A government spokesman said that two MiG23s of the Indian Air Force escorted the transport plane as a sign of respect to the assassinated prime minister.

The ashes had been transferred from copper urns to packages of red tissue paper and kept in wicker baskets on a flower-bedecked platform aboard the transport plane.

The prime minister dropped them in two phases, the first beginning at Gangotra, where the Bhagirathi River forms the headwaters of the Ganges, and the second between Nun Kun and Amarnath, the tissues bursting open in the plane's slipstream. Along the route are places hallowed in the Hindu religion such as Badrinath and Kedarnath, both shrines to the gods Vishnu and Siva.

The slain prime minister had described Gangotri as the symbol of the earth's need for water.

The ceremonies began at sunrise at Teen Murti House, where Nehru lived and died, with a procession carrying three urns on a gun carriage to Palam Airport, where a helicopter waited to transport the mourners to Hindon Air Base. Since Monday, the urns had been kept at the Nehru house under a laburnum tree planted as a child by the slain prime minister's son, Sanjay, who died in a stunt plane accident in 1980. The remaining urns had been transported to Hindon Air Base from the states in which they had been displayed.