DHARAN, Nepal (AP) _ Monsoon rains Monday hampered rescuers trying to find bodies and help survivors of a powerful earthquake that killed at least 650 people in remote areas of Nepal and India.

The quake in the Himalayan slopes, foothills and valleys just before dawn Sunday registered 6.5 on the Richter scale and was the deadliest in the the India-Nepal border region since l950.

At least 450 people were reported killed and 1,000 injured in Nepal, and at least 200 dead and 2,000 injured in India.

Nepalese officials said damage surveys were being made but poor communications probably would delay a comprehensive casualty report until at least Wednesday.

Dharan, a city of 100,000 at the base of a steep slope, appeared to be hit hardest. Searchers had recovered 131 bodies from the collapsed or damaged houses by Monday, said police superientendent B.B. Singh.

''I think we got most of them,'' he sid. ''At least 100 houses in the town were flattened. Almost every house in the district has cracks. It will take years to rebuild the town.''

At a Dharan hospital, 18-year-old Krishna Budhathoki sat on a bed, his head and an ankle bandagedd, staring blankly at the wall.

''I got up and ran out of the house when the ground shook, but I went back because my mother was still inside,'' he said. ''When i tried to break open her bedroom, the house fell on me.'

Doctors said rescuers pulled Budhathoki from beneath a pile of bricks two hours later.

His mother survived with minor injuries, but his father, two sisters and a nephew died in the ruins of their wood and brick house in Dharan, 100 miles southeast of Katmandu, capital of Nepal.

Bir Bahadur Shahi, the home minister, toured the Dharan district Sunday and said 50,000-60,000 houses were destroyed.

Shahi said hundreds of people found shelter in guesthouses, schools and other public buildings. Tents were pitched on the sodden ground, Many people moved in with relatives or neighbours.

Shahi and other officials said water supplies remained adequate in the Dharan area and there were no reports of disease, but a doctor in Dharan city was less optimistic

The Dharan Hospital medical superintendent, who gave her name as C. Amathya, said she feared an outbreak of gastroenteritis, although no cases had been reported.

''Water supply to the town was cut off by the quake,'' she said. ''We have got some (water) tankers from Biratnagar, but they are not enough.'' Biratnagar is about 30 miles to the south, but the journey to Dharan takes two hours over muddy roads in which the earthquake made cracks a yard deep.

Rescue, search and relief efforts also were hampered in India, where many roads are poor even in the dry season. The area with the greatest damage and casualties was just below the border in Bihar, India's poorest state.

Landslides blocked many roads to devastated areas. Railroad tracks sank into the mud and the quake cracked bridges over rivers swollen by the monsoon.

Tremors flattened more than 25,000 houses in India, officials said. The Bhoothai Balan River flooded nearly 50 villages in the Madhubani district. Forty-five people were killed, but whether by floods or collapsing houses was not known.

Indian army soldiers helped with relief efforts, and the navy and air force were put on alert. Nepalese soldiers, police and volunteers joined forces in the kingdom's remote mountains and valleys.

Niranjan Thapa of the Home Minstry reported extensive damage in 21 of Nepal's 75 districts and at least four affected districts reported 50 or more deaths.

Officials distributed 88-pound bags of rice to families in the kingdom of 17 million people.

Government officials said many offers of assistance had come from abroad, but no decision had been made about whether to accept them.

A U.S. Embassy official said it had offered $25,000 in immediate aid but had not received a response.

The quake was the worst in the region since a temblor in India's eastern state of Assam killed 1,500 people in 1950, according to official accounts. Seismologists said their records showed a death toll of at least 30,000.

The Richter scale measures ground motion as recorded on seismographs and each number represents aa tenflod increaase in intensity. A quake of 6 on the scale is capable of causing severe damage and one of 7 can cause widespread, heavy damage.