The official death toll had been 255, but the surge in fatalities appeared to indicate rescuers had reached remote villages and that restoration of phone service was enabling better accounting, The Wall Street Journal reported.
Aquino, in a nationally televised address, spoke of relief operations and international help for his country, where estimates of the death toll from the monster typhoon are as high as 10,000.
"We have declared a state of national calamity in order to speed up the delivery of rescue, relief and rehabilitation efforts in the provinces devastated," the president said.
Haiyan struck the country Friday and went on to batter Vietnam.
Aquino said more funding was approved for the departments of Social Welfare and Public Works and Highways so they could help millions of affected people, the Philippine Daily Inquirer reported.
As the Philippines coped with the devastation caused by Haiyan, known locally as Yolanda, the country's weather service warned about another storm's approach.
While Haiyan pummeled Vietnam, causing heavy damage, weather officials said a tropical depression was forecast to make landfall in Surigao del Sur in the Philippines, Tuesday, the Daily Inquirer said.
"Hopefully it will stay that way or weaken after landfall," said Ruthie Manzanilla of Philippine Atmospheric Geophysical and Astronomical Services Administration.
Manzanilla told the Daily Inquirer the storm wouldn't be as strong as Haiyan, which leveled homes, cut off communications and destroyed transportation routes, making aid delivery and damage assessments difficult.
"There are too many people dead," Richard Gordon, chairman of the Philippine Red Cross, told CNN. "We have bodies in the water, bodies on the bridges, bodies on the side of the road."
Tacloban, a city of more than 200,000, was shattered by Haiyan, which brought a surge of water off the Gulf of Leyte. The storm surge flattened entire neighborhoods of wooden houses and tossed ships about as if they were toys.
With gusts topping 155 mph, Haiyan may have been the strongest tropical cyclone in recorded history, but meteorologists said more analysis was needed to confirm whether it set a record, CNN said.
After pummeling the Philippines, the storm lost some of its punch as it moved across the South China Sea during the weekend.
Early Monday, it hit the coast of northern Vietnam, 2 hours ahead of its expected landfall, the newspaper Tuoi Tre reported.
Authorities evacuated hundreds of thousands of people from vulnerable areas in preparation of Haiyan's arrival.
After Haiyan moved through Quang Ninh province, officials said three people were reported missing. They were aboard a cargo ship that sank during the storm. Rescuers saved one other crew member, authorities said.
Vietnamese officials said the storm destroyed 18 houses, ripped off 525 roofs, sank 16 ships, wrecked two antenna towers, uprooted numerous trees and damaged many acres of crops.
The storm moved into China's southern Guang Xi province, where it was predicted to weaken to a tropical depression, Tuoi Tre said.
Aid workers said Vietnam likely avoided the level of damage suffered by the Philippines but officials warned that heavy rains could cause flooding and landslides in northern Vietnam and southern China, CNN said.
In the Philippines, officials tried to establish the level of destruction at Tacloban and elsewhere along Haiyan's path.
On Samar island, where Haiyan made its first of six landfalls as it skipped across the islands, government and aid officials said they were still trying to reach many affected communities, as well as areas on Cebu and Panay islands.
Aid on military planes was arriving at Tacloban's airport, which resumed a very limited commercial flight schedule Monday, CNN said.
U.S. Marines, sent to assist in relief efforts, also arrived Monday in Tacloban.
"We're working hand-in-hand with the Philippines, both with their armed forces and the national police, and we will help them in their need," Brig. Gen. Paul Kennedy said.
But with roads blocked by downed trees and power lines and airports destroyed, relief efforts are challenged logistically, said Praveen Agrawal of the U.N. World Food Program
The lack of food and water led to looting and the threat by business owners to shoot intruders if necessary, CNN said.
Orla Fagan, spokeswoman for the U.N. Office for the Coordination of Humanitarian Affairs in Manila, estimated 9 million people were affected by the storm, Voice of America reported.
Besides food and water, she said a major concern was shelter because the Philippines is in its rainy season. She said several countries and humanitarian organizations have contributed money or materials for housing, as well as medical and rescue teams.
In his address, Aquino said 22 countries, as well as private organizations, either provided or pledged to provide aid and support for relief operations in the devastated areas, the Daily Inquirer said.