More than 600,000 people were evacuated as super typhoon Haiyan veered towards Vietnam, authorities said on Sunday, after the storm smashed through the Philippines killing thousands and causing widespread devastation.

Residents of the Vietnamese capital Hanoi were braced for heavy rains and flooding, while tens of thousands of people in coastal areas were ordered to take shelter ahead of Haiyan’s expected landfall on Monday morning.

“We have evacuated more than 174,000 households, which is equivalent to more than 600,000 people,” an official report by Vietnam’s flood and storm control department said on Sunday.

The storm is now expected to strike on Monday morning after changing course, prompting further mass evacuations of some 52,000 people in northern provinces by the coast, the VNExpress news site reported.

“People must bring enough food and necessities for three days... Those who do not move voluntarily will be forced,” the report said, adding all boats have been ordered ashore.

The Red Cross said in a statement Haiyan’s changed path meant “the disaster area could be enlarged from nine provinces to as many as 15” stretching the country’s resources.

“This is one of the challenges going ahead,” Michael Annear, Red Cross country representative, told AFP, adding that heavy rains and flooding were likely to hit Hanoi.

Reports on social media indicated many of the capital’s residents were rushing to markets to stock up on food and drinking water before the storm hit.

Many of the estimated 200,000 people evacuated in four south-central provinces initially thought to be in the storm’s path have been allowed to go back to their homes, according to a report on the government’s website.

Haiyan “is quickly moving north and northwest, travelling at a speed of up to 35 kilometres per hour”, the country’s weather bureau said in a statement.

At least four people were reportedly killed while preparing to escape the typhoon, disaster officials said.

By lunchtime on Sunday the typhoon had swept across Vietnam’s Con Co island, some 30 kilometres off the coast of central Quang Tri province, the Tuoi Tre newspaper reported.

“All 250 people on the island including residents and soldiers were evacuated to underground shelters where there is enough food for several days,” the report said, adding the storm brought three-metre high waves.