Anger mounted Wednesday over the slow pace of rescue operations in Indian Kashmir as officials said they were "overwhelmed" by the scale of deadly flooding that has left hundreds of thousands stranded in the Himalayan region and neighbouring Pakistan.

The floods and landslides from days of heavy rains have now claimed more than 450 lives in both countries as emergency workers scrambled to rescue residents left marooned on rooftops and clinging to trees.

With many parts of Indian Kashmir's main city Srinagar still cut off days after the floods hit, residents and rescuers alike criticised the state government's response, with one military officer saying officials were nowhere to be seen.

On Wednesday it emerged that one rescue officer had been wounded in an attack by furious residents earlier in the week as anger boiled over.

National Disaster Response Force director general O.P. Singh told the NDTV news channel an "aggressive crowd" had tried to attack a rescue boat, injuring the officer.

While thousands of soldiers and other emergency workers stepped up operations in India's Kashmir Valley as waters started to recede, the region's top leader said he could understand people's anger.

"We have really been overwhelmed. We have been overwhelmed by the scale of the problem," Jammu and Kashmir state Chief Minister Omar Abdullah told the CNN-IBN network.

"Our ability to supply people has been hampered by the fact that we have been unable to reach those areas. There are large parts of the city where even boats have not been able to reach.

"I understand their anger and I don't grudge them on that anger. They have gone through an extremely difficult time," he said of the rising frustrations.

More than 200 people have died in the region's worst floods in more than half a century. In neighbouring Pakistan, another 256 people have been killed, with Punjab the worst-hit area and floods threatening to inundate more areas downriver.

Nearly 600,000 people have been affected there and crops destroyed, an official said.

In the city of Lahore, the death toll from a mosque collapse rose to 24, while a provincial minister said the heavy monsoon rains may have been a contributing factor.

- 'Where is my mama?' -

On a stretch of road in India's Srinagar, hundreds of exhausted residents, some clutching children, others plastic bags of belongings, walked to an army relief camp on higher ground, searching for food and water.

Salim Nabi, his wife and two sons, have been camped on the road for days, with only a plastic sheet for shelter, waiting for the waters to recede further so they can check on their flooded house.

"The situation is absolutely pathetic. We are wondering why exactly we voted for a state government that does nothing for us," Nabi told AFP.

Abdul Ahad Tantray has been caring for his three-year-old granddaughter for days, after his daughter handed her over to a neighbour but then became trapped herself in her house.

With no news of her fate and the waters still too high to reach the house himself, Tantray said he was helpless.

"She has been crying for her mother, 'Where is my mama?'," he said.

Local army commander Dinesh Singh said a lack of government officials on the ground was hampering the military's rescue and relief efforts.

"The biggest problem is there that is no presence from the state government," Singh told AFP. "We need them to organise the crowds and help with coordination on where to send the boats."

More than 400,000 people remain stranded, officials say. As well as searching for those still trapped, soldiers and emergency workers have been distributing tonnes of water, biscuits, medical and other relief.

Some 79 planes and helicopters have been deployed along with several hundred boats, and more than 76,500 people have been rescued so far, the defence ministry said.

Waseem Farooq and his family of nine were rescued by locals in a boat, after being stranded on the roof of their flooded Srinagar home.

"We could see people huddled on treetops who were rescued by helicopters," said Farooq, who is now camping at a shrine along with thousands of others.

Rescue chief Singh said efforts were being hamstrung by communication failures, with some phone networks still knocked out.