Yagi, according to meteorologists the most powerful typhoon to hit northern Vietnam in 30 years, downed bridges, tore roofs off buildings and damaged factories after making landfall on Saturday carrying winds in excess of 149 kilometres (92 miles) per hour.

Power blackouts caused major disruptions to factories in northern Vietnam, which is a major production hub for global tech firms such as Samsung and Foxconn.

The north was also battling serious flooding on Monday, with several communities partially underwater.

The storm killed 59 people in Vietnam, state media reported, 44 of them in landslides and flash floods. The death toll had earlier been put at 21.

Authorities said on Monday that 247 people had been injured.

"The (flooding) situation is very serious. We have ordered the discharge of water (from reservoirs)," Nguyen Hoang Hiep, deputy minister of agriculture and rural development, said in a statement.

"Localities must be active to support and ensure the safety of their people and assets."

At least 24 others were killed as Yagi tore through southern China and the Philippines before hitting Vietnam.

Some 1.5 million people were still without electricity in Vietnam on Monday and a major bridge across the swollen and fast-moving Red River collapsed in northern Phu Tho province.

Pictures on state media showed half of the 375-metre Phong Chau bridge gone.

Deputy Prime Minister Ho Duc Phoc estimated 13 people were missing, according to state news site VNExpress.

He said there were 10 cars and trucks, along with two motorbikes, on the bridge when it collapsed.

In the neighbouring province of Yen Bai, 2,400 households were forced to move to higher ground as the water level rose to dangerous levels.

Floodwaters reached a metre (three feet) high in parts of Yen Bai City on Monday.

Disaster authorities said 130 locations in 17 cities and provinces across Vietnam's north were at high risk of flooding and landslides.

- Blackouts -

Across northern Vietnam, 5.7 million people customers were hit by power blackouts on Saturday and Sunday, according to state utility EVN.

Vietnam is a crucial part of the supply chain for some of the world's most important companies and many key domestic and foreign-owned factories are located in the north.

Hong Sun, chairman of the Korean Chamber of Business in Vietnam, told AFP on Monday that the typhoon had been a "disaster" for businesses, particularly in the area of Haiphong, a port city badly hit by the typhoon.

"During the typhoon there was a blackout situation so some of them had to shut down their factories, which means they had to spend a lot of time and money to reinstall all the machinery," he said.

Susumu Yoshida from the Japan Chamber of Commerce and Industry said the roof of one electronics company had blown off and their products had been flooded.

Among the victims of the typhoon was a family of four killed after heavy rain caused a hillside to collapse onto a house in the mountainous Hoa Binh province.

Six people, including a newborn baby and a one-year-old boy, were killed in a landslide in the Hoang Lien Son mountains of northwestern Vietnam on Sunday afternoon.

Typhoons in the region are forming closer to the coast, intensifying more rapidly, and staying over land longer due to climate change, according to a study published in July.

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