In India’s Assam state, at least nine people were killed in the floods and 2 million saw their homes submerged, according to the state disaster management agency.
Lightning in parts of neighboring Bangladesh meanwhile killed nine people on Friday.
Both countries have asked their militaries for help as more flooding looms with rains expected to continue over the weekend.
The Brahmaputra, one of Asia’s largest rivers, breached its mud embankments, inundating 3,000 villages and croplands in 28 of Assam’s 33 districts.
“We expect moderate to heavy rainfall in several parts of Assam till Sunday. The volume of rainfall has been unprecedented,” said Sanjay O’Neil, an official at the meteorological station in Gauhati, Assam’s capital.
Several train services were canceled in India amid the incessant downpour over the past five days. In southern Assam’s Haflong town, the railway station was underwater and flooded rivers deposited mud and silt along the rail tracks.
India’s army has been mobilized to assist disaster response agencies in rescuing stranded people and providing food and other essentials. Soldiers used speedboats and inflatable rafts to navigate through submerged areas.
In Bangladesh, districts near the Indian border have been worst affected.
Water levels in all major rivers across the country were rising, according to the flood forecasting and warning center in Dhaka, the capital. The country has about 130 rivers.
The center said the flood situation is likely to deteriorate in the worst-hit Sunamganj and Sylhet districts in the northeastern region as well as in Lalmonirhat, Kurigram, Nilphamari and Rangpur districts in northern Bangladesh.
Flight operations at Osmani International Airport in Sylhet have been suspended for three days as floodwaters have almost reached the runway, according to Hafiz Ahmed, the airport manager.
Last month, a pre-monsoon flash flood, triggered by a rush of water from upstream in India’s northeastern states, hit Bangladesh’s northern and northeastern regions, destroying crops and damaging homes and roads. The country was just starting to recover when fresh rains flooded the same areas again this week.
Bangladesh, a nation of 160 million people, is low-lying and faces threats from natural disasters such as floods and cyclones, made worse by climate change. According to the U.N.’s Intergovernmental Panel on Climate Change, about 17% of people in Bangladesh would need to be relocated over the next decade or so if global warming persists at the present rate.
More Must-Read Stories From TIME