Pakistan evacuated at least 150,000 people in areas along three rivers in its agricultural heartland under threat of flooding after neighbouring India warned it plans to release excess water from a dam, officials said on Tuesday.

The arch-rivals have been ravaged by intense rain and flooding in recent weeks. The release of excess water threatens to further inundate part of Pakistan's Punjab province, which serves as the country's breadbasket and accounts for a large part of its food supply.

The nuclear-armed nations have been in a tense stand-off since a brief conflict in May, their worst fighting in decades, and any flooding blamed on New Delhi could inflame ties.

Pakistani officials said they received a surprise warning from India on Monday that it intends to release water from the rapidly filling Madhopur Dam, on its side of Punjab province.

India routinely releases water from its dams when they get too full, with the excess flowing into Pakistan.

An Indian government source said they had not mentioned a specific dam but the intense rain led them to share a second warning with Pakistan through diplomatic channels. Asked if more warnings could be issued as rain continues, he said it was possible.

New Delhi had said on Sunday that it warned Pakistan that large volumes of water would flow into its waterways due to the heavy rainfall.

Three rivers - Ravi, Sutlej and Chenab – flow into Pakistan from Indian territory. Those rivers are seeing medium to high flooding, Pakistan's National Disaster Management Authority said on Tuesday.

Mazhar Hussain, a Pakistani disaster management official, said India will release a controlled amount of water from dams in the coming days. Hundreds of villages situated on the embankment of the three rivers have been evacuated, he said.

AGRICULTURAL HEARTLAND

Pakistan's northwest has been hammered by intense floods, accounting for half of the 799 people killed this monsoon season.

The northern region of Gilgit Baltistan has suffered accelerated glacial melting, while the southern city of Karachi was partly submerged last week.

Now the worst of the flooding is threatening the eastern province of Punjab, home to half of Pakistan's 240 million people.

The province produces the majority of Pakistan's staple crops and the areas along the three rivers boast large tracts of fertile agricultural lands.

The warning from India on Sunday came after New Delhi put in abeyance a decades-old treaty with Islamabad on sharing water from the Indus river network. India suspended the treaty after blaming Pakistan for a deadly attack on Hindu tourists in Indian Kashmir, which sparked the hostilities in May.

Islamabad denied any involvement.

An Indian official said on Sunday that the warning was shared with Pakistan's foreign ministry on "humanitarian grounds", and not under the 1960 Indus Waters Treaty, following heavy rains in the northern Jammu and Kashmir.

Floods in the region have killed at least 60 people this month.

Pakistan's foreign ministry said the warning was issued through diplomatic channels "rather than through the Indus Waters Commission as required under the Indus Waters Treaty".