KATHMANDU: Flash floods and landslides in Nepal triggered by monsoon rains killed 15 people and injured 12 overnight while another 18 have gone missing, officials said on Saturday.

The latest deaths took to 30 the number of people killed in incessant rain that since Thursday has pounded much of the Himalayan nation tucked between China and India.

Officials said the Kosi River in eastern Nepal, which flows into the eastern Indian state of Bihar, had risen above the danger mark.

The Kosi has been a serious concern for both India and Nepal since it broke its banks in 2008 and changed course, submerging swathes of land and affecting more than two million people in Bihar. About 500 people died in that disaster.

Thirty of the 56 sluice gates at a barrage along the Kosi at the Indo-Nepal border have been opened, and rescue teams deployed to evacuate villagers, officials said.

The weather office urged residents to remain alert, saying heavy rains were expected to continue through the weekend.

"Though rains have eased in some areas, people should remain very careful as there are chances of heavy rains through Sunday," weather department official Bibhuti Pokharel told Reuters.

The annual monsoon rains, which normally start in June and continue through September, are crucial for Nepal, a country of 30 million people, and India, which both depend on the annual downpours for farming. But landslides and floods often result, killing scores of people every year.