Philippine President Ferdinand Marcos Jr conducted an aerial survey of damage brought on by typhoon Noru, which left heavy flooding across several northern provinces as authorities rushed to get aid to thousands of evacuees.

Governor Daniel Fernando declared that five rescue workers were killed in Bulacan province, while local residents were seen wading through waist-deep waters, with others stranded on rooftops.

Floods submerged swathes of farmland and communities in the north, video and images shared by the president's office showed, after the category 3 typhoon dumped heavy rains and brought strong winds after making landfall at the weekend.

President Marcos ordered supplies to be airlifted and equipment be provided to help the clean-up in worst-affected communities. He also directed officials to provide emergency power to cut-off areas.

“They were living heroes who were helping save the lives of our countrymen in the calamity,” Gov. Fernando said. “This is really very sad.”

Paying tribute to the rescuers on social media, the Bulacan police force said on social media: “They showed bravery and heroism in facing danger despite the perils to their own lives to fulfil their duty of saving other people,”

Typhoon Noru weakened after passing through the Philippines on Sunday night and was headed out over the South China Sea towards Vietnam, where authorities were racing to prepare for its arrival.

The government has warned of the threat of Noru, anticipating what it said was one of the biggest typhoons to hit Vietnam in 20 years.

"This is the worst flooding that happened here," resident Elpidio dela Cruz told Reuters in Bulacan, standing knee-deep in water outside his house.

"The water reached the second floor," he added.

Another Bulacan resident, Teody Simbulan, appealed for aid. "People here need help like food, water and medicine," he added.

An archipelago of more than 7,600 islands, the Philippines sees an average of 20 tropical storms yearly. In 2013, Typhoon Haiyan, one of the most powerful tropical cyclones ever recorded, killed 6,300 people.

Photos from state media showed people rushing to fortify homes, anchor boats and stock up on food.

Schools have been closed and boat owners ordered to stay ashore in central provinces, while the government said it was ready to evacuate about a million people if necessary.