Pakistan: Torrential rain and floods paralyse Karachi
Pakistan's commercial capital, Karachi, has been paralysed by floods as torrential rain continues to lash southern Sindh province.
Schools have shut down, many markets were forced to close and commuters had to abandon their vehicles as rain water flooded the streets.
Villages across the province have been inundated as canals have been breached and water has not adequately drained.
Many in the region are still recovering from last year's devastating floods.
Millions were displaced across the country and about 2,000 people died as torrential monsoon rains in 2010 caused rivers to burst their banks, washing away homes and property. Sindh was one of the worst affected regions.
Some aid officials have said this year's flood situation is as bad as the devastation last year.
Then, a vast body of water flowed down the country, bursting the banks of the River Indus and hitting surrounding areas. This year's floods are caused by rainfall - two weeks of it so far - so the impact is far more widespread.
Pakistan's disaster management chief warned on Monday that the situation is worsening each day as water levels are rising because of poor drainage.
Almost one million houses in Sindh have been destroyed or damaged and floods have affected nearly 4.2m acres of land, the UN says.
Many people are living in temporary shelters or out in the open. Stranded families need food and drinking water but can be reached only by boat or helicopter.
Officials say more than five million people have been affected by the flooding, which has so far killed 260 people.
"We're seeing right now that 22 out of 23 districts are affected," Andro Shilakadze, who works for the United Nations children's fund (Unicef) in Sindh, told the BBC.
"So far there is a displacement. We don't have exact information but not all of them are in camps. Some of these people resist leaving their dwellings and are standing on the road in temporary shelters to look after their cattle."
The US has already send food aid. It is also promising tents, medicine and other non-food items.
China has pledged $4.7m (£2.96) for urgent humanitarian assistance.
On Monday the UN said it had begun efforts to feed 500,000 people affected by the floods and rain, initially concentrating its efforts in Sindh's badly-hit Badin district.
The BBC's Jill McGivering says there has been criticism of the government's failure to repair flood defences which were breached last year. Some analysts say if that work had been done, the damage now would be limited.
'I am stuck'
In Karachi, the capital of Sindh, many streets were flooded and impassable to vehicles.
"I thought I would be able to make it to work, but it was a wrong decision. Now I am stuck. My car has broken down and I can't even find anyone for help," banker Khalid Hussain told Reuters news agency.
Many main roads have been inundated and the situation could become worse, the city's district co-ordinator told Reuters. Karachi's stock exchange was set to close early, but one report said it had reversed this plan.
Neighbouring India has also been affected by heavy monsoon rain.
The government in India's eastern Orissa state has intensified its efforts to deliver aid as more than one million people were displaced and at least 16 killed by floods in recent days.
About 2,600 villages have been submerged across 19 districts and 11 people are missing.
Officials there say the rains have eased somewhat but more is forecast for the coming days.