India's 15 million Sikhs, still stunned by attacks by Hindu mobs that left more than 1,000 dead after the assassination of prime minister Indira Gandhi, held subdued observances today to mark the 515th anniversary of the birth of the founder of their religion, Guru Nanak.

Paramilitary security forces and Indian Army troops guarded Sikh temples in New Delhi, some of them damaged in the sectarian rioting, as devotees offered prayers and participated in the langar, the traditional free meal offered at Sikh holy places.

To avoid provoking Hindus, Sikh priests canceled the traditional processions through city streets. Attendance at some temples was sparse, apparently because many Sikhs were afraid to travel.

No incidents of violence were reported in New Delhi or elsewhere in the country.

The Associated Press reported that about 50,000 worshipers, only one-fifth of the crowd in past years, offered prayers at the Golden Temple in Amritsar under heavy guard by police and Army troops. The Golden Temple is the holiest shrine of the Sikh religion.

At the Bangla Sahib Temple here, several hundred Sikhs milled around a courtyard, talking of the wave of arson and murder that followed Gandhi's assassination and watching the security forces lounging in the shade of nearby trees.

"Today nothing will happen, because there are so many press reporters around. But sooner or later, it will happen again," said Rajinder Singh. "How can we feel safe when our property has been looted, our honor taken away and our families killed?"

Similar expressions of bitterness were voiced by other Sikhs. including some who said they never before supported a separate Sikh state but do so now. Some invoked the name of Jarnail Singh Bhindranwale, the separatist guerrilla leader who was killed in the June 5 Army assault on Amritsar's Golden Temple complex. "At this moment, we remember Bhindranwale and how he always told us to buy revolvers to protect ourselves. He knew this day would come. He said, 'Beware, you must buy guns.' He was right," said a Sikh bus driver, who would not give his name because, he said, he feared arrest.

"It's not finished. Sikhs should buy Sten guns, because any mob can kill us now. We can only feel secure if we have Sten guns in our hands," he said.

Sikhs who had taken shelter in refugee centers here continued to return to their neighborhoods and, in some cases, their damaged homes. Army troops were deployed in about 15 religiously mixed neighborhoods to guard Sikh homes at the request of the occupants, said Maj. Gen. J.S. Jamwal, the Delhi area commander.

Meanwhile, Prime Minister Rajiv Gandhi was scheduled to take an urn containing the ashes of his mother, who was cremated Saturday, to her birthplace in Allahabad on Friday.

Other urns of ashes sent to all states and union territories earlier in the week for public viewing will be returned to the capital Friday. On Sunday, Gandhi will scatter the ashes over the Himalaya Mountains in Kashmir, the ancestral home of the Nehru family. A portion will be strewn at Gangotri, the source of the Ganges River.