SRINAGAR, India (AFP) -- The death toll from devastating floods in India and Pakistan rose to 400 on Tuesday with hundreds of thousands more stranded, some "neck-deep" in water, authorities said.

A huge rescue effort is under way in the divided mountainous region of Kashmir after monsoon rains submerged hundreds of villages, in the deadliest flooding there in over half a century.

Rajesh Kumar, police inspector general for the Jammu region on the Indian side, said Tuesday the toll had risen to around 200.

Another 206 people are confirmed dead on the Pakistan side.

"The situation in the Kashmir valley is still very grim, it is quite critical," Kumar told AFP.

"The main highway is still cut off from everything. But thankfully, many other road networks have been restored to a large extent."

The Press Trust of India (PTI) news agency said an estimated 400,000 people remained stranded in flood-hit areas on the Indian side.

"We are facing a shortage of boats for rescuing people from inundated areas," the divisional commissioner for Kashmir, Rohit Kansal, told PTI.

"A lot of 100 boats is being airlifted from Delhi which shall be landing here any moment."

Kumar said he could not say exactly how many were stranded, but that "there are many stuck in neck-deep water and need help as soon as possible".

Some water and electricity lines had been restored in areas that were less severely affected, he added.