ISLAMABAD, Aug 9 The number of people suffering from the massive floods in Pakistan exceeds 13 million - more than the combined total of the 2004 Indian Ocean tsunami, the 2005 Kashmir earthquake and the 2010 Haiti earthquake, the United Nations said on Monday.

The death toll in each of those three disasters was much higher than over 1,500 people killed so far in the floods that first hit Pakistan two weeks ago. But the UN estimates that 13.8 million people have been affected - over 2 million more than the other disasters combined.

The comparison helps frame the scale of the crisis, which Prime Minister Yousuf Raza Gilani said on Monday was the worst in Pakistan's history.

“The number of people affected by the floods is greater than the other three disasters combined,” Maurizio Giuliano, spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA), told The Associated Press.

A person is considered affected by the floods if he or she will need some form of assistance to recover, either short-term humanitarian aid or longer-term reconstruction help, said Mr Giuliano.

The total number of people affected in the three other disasters was about 11 million - 5 million in the tsunami and 3 million in each of the earthquakes - said Mr Giuliano.

Many of the people affected by the floods, which were caused by extremely heavy monsoon rains, were in the province of Khyber Pakhtunkhwa.

“All these people are in very serious need of assistance, and we are highly concerned about their situation,” said Mr Giuliano.

A senior government official in Sukkur, Inamullah Dhareejo, said authorities were working to set up relief camps in the district and deliver food to victims.

But an Associated Press reporter who travelled widely through the worst-hit areas in Sindh over the past three days saw no sign of relief camps or government assistance.

Amin Ahmed adds An OCHA situation report released on Monday said that the UN body was setting up a 'humanitarian coordination centre' in Islamabad to boost relief assistance to flood victims and rehabilitation of the affected areas.

The OCHA has reinforced its field assessment and coordination capacities in Punjab and Sindh. In KP, the World Food Programme completed assessment of the damage in 11 districts.

In the next few days, the focus will be on assessing the situation in flood-hit areas of Sindh and Punjab and strengthening the overall capacity to coordinate assessments and expedite the distribution of urgently needed assistance.

The Food and Agriculture Organisation also began on Monday an assessment of the damage caused to the agricultural sector in the nine most affected districts of KP.