While 15 people have been killed in floods and landslides and over 46 lakh have been affected in Assam, 24 deaths have been reported from north Bihar, which is facing a serious flood situation as water levels of rivers in the area continue to rise.

In the northeast, the situation was also grave in Tripura and Mizoram where incessant rains have cut the two states off from the rest of the country and led to thousands of people taking shelter in relief camps.

Prime Minister Narendra Modi on Monday spoke to Assam Chief Minister Sarbananda Sonowal over phone and took stock of the ongoing flood situation in the state. He also assured of all help to the state, according to a statement from the Chief Minister's Office.

An official of the Assam State Disaster Management Authority said that 4,175 villages, with 46.28 lakh people, have been affected due to the floods, as of Monday afternoon, while close to 90,000 hectares of agricultural lands are inundated.

The government has pressed the National Disaster Response Force and State Disaster Response Force to help the marooned people in different districts while the Army has been called in to assist the civil administration in relief and rescue operations.

Over 10 lakh animals have also been affected. Almost 90 percent of the Kaziranga National Park has been submerged and authorities are taking various measures, including speed restrictions on NH 37 which touches the park, to save animals as they head to higher ground to save themselves.

In Tripura and Mizoram, over 22,000 people have been shifted to relief camps and other safer places due to flooding of low-lying areas and villages by uninterrupted rains over the past three days, officials said on Monday.

Train services between the states and the rest of the country have been affected due to rain and landslides, while water, electricity and telephone services were badly affected due to damages in the heavy downpour.

India Meteorological Department Director Dilip Saha, however, told IANS that the situation is expected to improve from Tuesday.

According to officials in Tripura Disaster Control Centre, over 17,000 people have taken shelter in 64 relief camps on the outskirts of Agartala and four other districts - Khowai, Unokoti, Gomati and South Tripura.

The body of a youth who had apparently drowned while collecting wood from the flooded Muhuri river in South Tripura was recovered on Sunday, officials said.

In Mizoram, over 5,000 people have taken shelter in safer places in different districts as major rivers and their tributaries submerged over 500 houses and low-lying areas.

Three people, including a 5-year-old girl, drowned in different rivers and their bodies were recovered.

In north Bihar, the flood situation grew serious as water levels of rivers in the area continued to rise, with many like the Bagmati, Kamala and Mahananda crossing the danger mark at various places, and the Kosi and Gandak also brimming

The worst-affected districts are Araria, Kishanganj, Supaul, Darbhanga, Sheohar, Sitamarhi, East Champaran, Madhubani, Muzaffarpur, Purnea and Saharsa. According to official reports, over 25 lakh people in 546 panchayat areas of 77 blocks have been affected.

Chief Minister Nitish Kumar, who had made an aerial survey of some of the affected areas on Sunday, made another aerial survey of submerged areas in Araria, Kishanganj and other districts. He later directed officials to speed up relief and rehabilitation measures.

The Disaster Management Department said 19 companies of the National Disaster Response Force and the State Disaster Response Force have been deployed in the area.

An official said that 152 relief camps have been set up, and are housing over 45,000 people.

However, in Sitamarhi, a group of affected people said that they are yet to see any relief and rescue measures in the area.

Heavy rains across Uttarakhand on Monday continued to affect normal life and led to an 'orange' alert - the second-highest category of weather warning - being issued across the hill state.

The rain led to landslides at various places, including the Gangotri Highway, while two houses collapsed in Chamoli district, but no injuries were reported as luckily the houses were then empty.

While the India Meteorological Department has advised people not to travel to higher reaches of the state, the State Disaster Response Force has been put on a 24-hour alert on the 'Char Dham' Highway.

The Char Dham Highway has been hit by the monsoon, with the roads being blocked by rain and the landslides, surface subsidence, cuts and overflowing rivers.

The Rishikesh-Gangotri highway remained blocked due to a landslide in Tehri district's Tachla area.

In Haldwani, the gateway to the Kumaon region, incessant rain led to the irrigation channels and the drains getting choked, leading to the mud and slush overflow onto the roads and into houses.

No respite seems in sight as the IMD has predicted heavy rains in most parts of the state. In Haridwar, the district administration has ordered all government and private schools and colleges to remain shut following warnings of heavy rains in the area in the 24 hours.