At least 28 killed after Vietnam tourist boat capsizes in Ha Long Bay

At least 28 people have been killed and over a dozen others are feared missing after a tourist boat carrying families capsized in Vietnam's iconic Ha Long Bay on Saturday.

State media reports indicate that the vessel, with 48 passengers and five crew members on board, overturned due to sudden heavy rain in the UNESCO World Heritage site.

According to the Dan Tri news site, the tragic incident unfolded swiftly, catching the boat off guard. The VNExpress further reported that the majority of those on board were families visiting from the capital city of Hanoi, with over 20 children among the passengers.

"Border guards rescued 12 people and recovered 18 bodies," it added, as search and rescue efforts were expected to continue into the night to find the dozens still missing.

Prime Minister Pham Minh Chinh sent his condolences to the families of the deceased and called on the defence and public security ministries to conduct an urgent search and rescue.

Authorities would "investigate and clarify the cause of the incident and strictly handle violations", a statement on the government website said.

Tran Trong Hung, a resident in the Ha Long Bay area, told AFP: "The sky turned dark at around 2pm."

There were "hailstones as big as toes with torrential rain, thunderstorm and lightning", he said.

Torrential rain also lashed northern Hanoi, Thai Nguyen and Bac Ninh provinces on Saturday.

In the capital, Hanoi, several trees were knocked down by strong winds.

The storm followed three days of intense heat, with the mercury hitting 37 degrees Celsius in some areas.

Mai Van Khiem, director of the National Centre for Hydrometeorological Forecasting, was quoted in VNExpress as saying that the thunderstorms in northern Vietnam were not caused by the influence of Tropical Storm Wipha in the South China Sea.

Ha Long Bay is one of Vietnam's most popular tourist destinations, with millions of people visiting its blue-green waters and rainforest-topped limestone islands each year.

Last year, 30 vessels sank at boat lock areas in coastal Quang Ninh province along Ha Long Bay after Typhoon Yagi brought strong winds and waves.

Earlier this month, a ferry sank off the popular Indonesian resort island of Bali, killing at least 18 people.