TACLOBAN, Philippines (CNN) -- A day after Super Typhoon Haiyan roared into the Philippines, officials predicted that the death toll could reach 1,200 -- or more.
"We estimate 1,000 people were killed in Tacloban and 200 in Samar province," Gwendolyn Pang, secretary general of the Philippine Red Cross, said of two coastal areas where Haiyan hit first as it began its march Friday across the archipelago.
The Red Cross said it would have more precise numbers Sunday.
The government's official toll as of Saturday evening was 138 dead, 14 injured and four missing.
But experts predicted that it will take days to get the full scope of the damage wrought by a typhoon described as one of the strongest to make landfall in recorded history.
"Probably the casualty figure will increase as we get more information from remote areas, which have been cut off from communications," said Tomoo Hozumi, UNICEF's Philippines representative.
The casualties from the storm, which affected 4.3 million people in 36 provinces, occurred despite preparations that included the evacuation of more than 800,000 people, he said.
On Saturday, more than 330,000 people were still in 1,223 evacuation centers, and the government had accepted a U.N. offer of international aid.
The National Risk Reduction and Management Council said more than 70,000 families were affected, and nearly 350,000 people were displaced -- inside and outside evacuation centers. Thousands of houses were destroyed, it said.
Tacloban hardest hit
Tacloban suffered the greatest devastation, said Lt. Jim Aris Alago, information officer for Navy Central Command. "There are numbers of undetermined casualties found along the roads."
Officials found more than 100 bodies scattered on the streets of the coastal city.
"We expect the greatest number of casualties there," Alago said, adding that 100 body bags had been sent to the area. People were wading through waist-high water, and overturned vehicles, downed utility poles and trees were blocking roads and delaying the aid effort.
Mobile services were down, and officials were relying on radios.
Another 100 residents in this city of 220,000 were injured, said Capt. John Andrews, deputy director of the national Civil Aviation Authority.
Roofs and windows were blown off of and out of many of the buildings left standing. Rescue crews were handing out ready-to-eat meals, clothing, blankets, medicine and water, Alago said.
But the speed of the storm -- which was clocked at 41 mph -- meant residents didn't have to hunker down long. Many emerged Saturday from their homes and shelters and trekked through streets littered with debris to supermarkets, looking for water and food. Several bodies were found at a chapel; a woman wept over one.
The Philippine Red Cross succeeded in getting its assessment team in to Tacloban but had not managed to get its main team of aid workers and equipment to the city, said Philippine National Red Cross Chairman Richard Gordon.
"We really are having access problems," he said.
The city's airport was shut to commercial flights, and it would be three days before a land route was open, so organizers were considering chartering a boat for the 1½-to-2-day trip, he said.
"It really is an awful, awful situation."
Tacloban, on Leyte island, is the largest city in the Eastern Visayas Islands. It was an important logistical base during World War II and served as a temporary capital of the Philippines.
Some hospitals on Leyte were destroyed, the official Philippines News Agency reported, adding that the Department of Health had sought help from the World Health Organization.
The destruction across the islands was catastrophic and widespread. For a time, storm clouds covered the entire Philippines, stretching 1,120 miles -- the distance between Florida and Canada -- and tropical storm-force winds covered an area the size of Germany.
A representative of the humanitarian organization CARE in the Philippines said the agency was trying to bring in supplies but did not know where they might be most needed. "We haven't heard anything from the municipalities on the Pacific side," Celso Dulce said.
The storm first struck before dawn on Friday on the country's eastern island of Samar, flooding streets and knocking out power and communications in most of Eastern Visayas region.
Powered by 195-mph winds and gusts up to 235 mph, it then struck near Tacloban and Dulag on the island of Leyte, flooding the coastal communities.
"It is like a tsunami has hit here," CNN's Paula Hancocks said from Tacloban.
Many islands hit
Haiyan continued its march, barreling into five other Philippine islands before its wind strength dropped Saturday to 130 mph and it lost its super typhoon designation.
On Friday, the Red Cross had more than 700,000 people in evacuation centers, but some of those proved no match for the storm, the Red Cross' Gordon said. "People died there as well."
Meteorologists predicted that Haiyan would weaken to a minimal typhoon or a tropical storm before making landfall Monday morning in northern Vietnam between Hanoi and Vinh. Up to 12 inches of rain were forecast for portions of northern Vietnam near the border with China by Monday night.
By late Saturday, Philippine military helicopters were taking surveys of the disaster; it took relief workers from Manila up to 18 hours to reach the worst-hit isles.
Super Typhoon Haiyan packed a wallop on Philippine structures that was 3.5 times more forceful than the United States' Hurricane Katrina in 2005, which directly or indirectly killed 1,833 people. At $108 billion, it was the costliest hurricane in U.S. history.
Haiyan may be the strongest tropical cyclone in recorded history, though meteorologists said it will take further analysis to establish whether it is a record.
Most of Cebu province couldn't be contacted by landlines, cell phones or radio, Dennis Chiong, operations officer for the province's disaster risk and emergency management, said Saturday.
One inaccessible town, Daanbantayan, has more than 3,000 residents who "badly need food, water and shelter because most of the houses there are damaged due to the storm," Chiong said.
In the town of Santa Fe in Cebu province, officials could not determine the number of fatalities because roads were washed out and phone services down.
Defenseless against the storm's might
One major concern was the typhoon's impact on Bohol Island, where 350,000 people had been living in tents and temporary shelters since last month's earthquake, said Joe Curry of Catholic Relief Services.
But he said he was concerned about other areas, too.
"There are a lot of rural areas, a lot of small islands that are affected," Curry said. "We don't know how they can protect themselves from a typhoon of this strength."
Clarson Fruelda of Cebu City said residents were cleaning up dirt, leaves, coconuts and tree branches from their homes.
"The winds were the strongest that I felt in more than 20 years," Fruelda said. "These past few weeks were really tough for my wife and I and probably for Cebuanos as well since it was just a few weeks ago when we were hit by a 7.2-magnitude earthquake."