Ten days of torrential flooding in Pakistan has affected more people than January's earthquake in Haiti, the 2005 earthquake in Kashmir, and the 2004 Asian Tsunami combined, according to the United Nations.

The U.N. estimates that some 13.8 million people –nearly 8 percent of the country's population- have been affected by the current floods, nearly 2 million more than the number affected by the previous disasters combined.

And while death tolls were much higher in the previous disasters than the 1,600 killed in Pakistan so far, the U.N. says that humanitarian needs appear to be on a similar level.

Flood waters have inundated a near 600-mile stretch of land down the center of Pakistan, with the most severely affected areas being the northwest province of Khyber Pakhtunkhwa, where 919 people alone have died, Baluchistan in the southwest, and the South Punjab provinces.

Continuing rains have hampered relief efforts, preventing helicopters from flying into regions that are unreachable by ground, including the Swat Valley, where the Pakistani government believes some 600,000 people remain stranded.

Several agencies have raised alarm over the possible spread of water-borne diseases, although no outbreaks have been reported yet.

Despite the massive damage, many Pakistanis refuse to leave their homes, as they fear losing their livestock and other possessions which constitute their livelihoods.

"This buffalo is worth 100,000 rupees ($1,000). It's my life's saving," one farmer told Reuters.

Others have expressed anger at the government for what they see as a failed relief effort.

"It would have been better if we had died in the floods as our current miserable life is much more painful," one victim told the Associated Press.

Meanwhile, the United Nations has said that billions of dollars are needed to reach the needs of flood victims.

As of Monday, nearly $45 million has been donated to the relief effort out of a pledged $91 million.

The United States alone has pledged more than $35 million and is providing other assistance such as rescue boats, water filtration units, and food assistance.

The U.N. says the most urgent need is shelter to protect those left homeless from the continuing rains.