United Nations aid agencies have provided assistance to hundreds of thousands of victims of Pakistan's worst floods in decades but relief operations have yet to reach an estimated six million people.

Tens of thousands of police and paramilitary soldiers patrolled the streets in Indian-controlled Kashmir as security was tightened across most parts of the region today a day after government forces killed four people during protests against Indian rule.

Leading charities have attacked the international response to the worst natural disaster in Pakistan's history, saying delays in funding the relief effort had affected aid operations.

The UN has asked Indian forces cracking down on separatist protests in Kashmir to stop wearing the distinctive blue helmets of UN peacekeepers.

Record water levels were pressing down on a crucial flood barrier in Pakistan's Sindh province last night as monsoon rains showed no sign of easing – adding to the vast surge of water bearing down on towns and villages.

Pakistan's navy sailed to the rescue of people stranded by devastating floods yesterday, while in India rescuers dug through destroyed homes and piles of mud after huge landslides in the remote north of the country killed about 130 people and left more than 500 missing.

Downpours are preventing helicopters from rescuing stranded people and delivering badly needed food and clean water

The hospitals are filling up with gunshot victims but angry protesters say the world is blind to their plight. Andrew Buncombe reports from Srinagar

The visit began inauspiciously, but the Prime Minister's famed charm and a sense of realism on the part of the President of Pakistan seem to have combined to salvage something for both sides.

Four people were killed after thousands of protesters ignored police warnings they would be shot on sight if they defied a round-the-clock curfew declared in Indian-controlled Kashmir, in an attempt to quell weeks of deadly civil unrest against Indian rule.

The worst floods in memory in Pakistan have devastated the lives of more than three million people, a UN spokesman said today while outrage over the unpopular government's response to its people's plight spreads.

Islamist charities, some with suspected ties to militants, stepped in today to provide aid for Pakistanis hit by the worst flooding in memory, piling pressure on a government criticised for its response to the disaster that has so far killed more than 1,000 people.

David Cameron will try to assuage Pakistani fury over remarks linking the country with terrorism after its president arrives for a visit to Britain tomorrow.