Super Typhoon Yagi ripped roofs off buildings, sank boats and triggered landslides in Vietnam, leaving nine people dead, before being downgraded into a tropical depression as it continues to weaken.

Yagi, which has devastated infrastructure and uprooted trees, made landfall in northern Vietnam, packing winds exceeding 149km/h (93 mph), before being downgraded into a tropical depression on Sunday. Meteorological authorities described Yagi as “one of the most powerful typhoons in the region” over the past decade.

A family of four was killed in a landslide in the mountainous Hoa Binh province of northern Vietnam early on Sunday morning, according to state media.

The landslide happened around midnight, after several hours of heavy rain brought by Yagi, when a hillside gave way and collapsed onto a house, VnExpress said, citing Vietnamese authorities.

The home’s 51-year-old owner escaped but his wife, daughter and two grandchildren were buried, their bodies recovered soon after.

Four people were also killed on Saturday as roofing flew through the air, disaster management authorities said.

A man in Hai Duong province was killed on Friday when strong winds brought down a tree.

Several areas of the port city of Hai Phong were under half a metre (1.6 feet) of floodwaters on Sunday, and electricity was out, with power lines and electric poles damaged, according to AFP news agency.

At Ha Long Bay, a UNESCO World Heritage Site about 70km (43 miles) up the coast from the city, fishermen were in shock as they examined the damage on Sunday morning.

According to the Reuters news agency, a dozen people were missing at sea near Ha Long, with rescue operations expected to start on Sunday when conditions allow. The report could not be immediately verified.

At least 23 boats were also seriously damaged or sunk at the Hai Au boat lock on Tuan Chau Island, according to residents.

Rooftops of buildings were blown off and motorbikes were left toppled over in piles of building rubble and glass, AFP reported.

Before hitting Vietnam, Yagi tore through southern China and the Philippines, killing at least 24 people and injuring dozens others.

Mounting evidence shows that increasingly warmer oceans are fuelling more powerful tropical storms than before, according to climate scientists.

Men collect debris on a flooded street after Super Typhoon Yagi hit the city of Hai Phong [Nhac Nguyen/AFP]