Philippine Red Cross secretary general Gwendolyn Pang said the figure of 1,200 was an estimate, with authorities yet to get an accurate assessment from many devastated communities.
"It's an estimate. Somebody else has to do the counting," Pang told.
Super Typhoon Haiyan tore into the eastern islands of Leyte and Samar on Friday with sustained winds of around 315 kilometers (195 miles) an hour, then tormented millions of people as it ripped across the Southeast Asian archipelago.
Energy Secretary Jericho Petilla flying to the devastated fishing town of Palo in Leyte by helicopter said he believed "hundreds" of people had died just in that area.
Petilla, a Palo native, was dispatched by President Benigno Aquino to survey the island and said there were similar scenes of carnage in three other cities or towns in Leyte.
"They all looked the same. The roofs were off all the buildings they were littered with fallen trees," he said.
Some of the worst-hit areas on Leyte and Samar, isolated by destroyed power and communication lines as well as damaged roads, had yet to be contacted.
More than four million people were affected across 36 provinces, the government said.
Aside from the ferocious winds, Haiyan generated storm surges that saw waves three meters (10 feet) high swamp coastal towns and power inland.
"This is destruction on a massive scale. There are cars thrown like tumble weed and the streets are strewn with debris," said Sebastian Rhodes Stampa, the head of a United Nations disaster assessment coordination team.
"The last time I saw something of this scale was in the aftermath of the Indian Ocean tsunami," he said, referring to the 2004 disaster that claimed about 220,000 lives.
Stampa made his comments after arriving in Tacloban, the destroyed capital of Leyte with a population of about 220,000 people that is about 10 kilometers from Palo.
More than 100 bodies were littered in and around Tacloban's airport, according to the facility's manager.
The military, government officials and relief workers raced to survey and provide aid to dozens of other communities across the path of destruction.
The Philippines suffered the world's strongest storm of 2012, when Typhoon Bopha left about 2,000 people dead or missing on the southern island of Mindanao.
RA/SHI