Typhoon Mangkhut is on course to hit north-eastern Cagayan province early on Saturday.
Chinese authorities have ordered about 6,000 boats to return to harbor, and evacuated thousands of offshore oil platform workers, the state news agency, Xinhua, said.
"They can't decide for themselves where to go", he said of the children, expressing frustration that the tragedy was not prevented.
Mangkhut, a Thai word for the mangosteen fruit, is the 15th storm this year to batter the Philippines, which is hit by about 20 a year and is considered one of the world's most disaster-prone countries. "His clear and concise marching order was 'Save lives, save lives, '" said Francis Tolentino, the government's disaster response coordinator and adviser to Philippine President Rodrigo Duterte.
More than 15,000 people had been evacuated in northern provinces by Friday afternoon, the Office of Civil Defence said. "Rivers usually swell after the storms".
Storm warnings remained in effect in 10 northern provinces, including Cagayan, which could still be lashed by devastating winds, forecasters said.
Gov. Bojie Dy reports more than 5,000 people have been evacuated from coastal areas in Isabela province.
Mangkhut is now some 220 kilometers (136 miles) south-southeast of the city, and heading for the surrounding Pearl River Delta, home to 120 million people.
"Almost all of the buildings here have been damaged, the roofs were blown away", Rogelio Sending, a government official in Tuguegarao, the capital of Cagayan, told Reuters.
Farms across northern Luzon, which produces a large portion of the nation's rice and corn, were sitting under muddy floodwaters, their crops ruined just a month before harvest.
The dead were two women killed in landslide, a girl who drowned and a security guard crush by a falling wall. The semiautonomous region is preparing for "fierce winds" and "intense" downpours as the storm moves west-northwest at roughly 8 miles per hour, according to the Hong Kong Observatory.
The city's observatory warned that Mangkhut would pass 100 kilometres south of Hong Kong at around midday local time as it raised the storm alert to its highest level.
As the storm heads for China's southern coast, Cathay Pacific said it expects more than 400 flight cancellations over the next three days.
Mangkhut will keep to a northwesterly track, bringing heavy rain and winds when it enters the autonomous region of Guangxi early on Monday, before weakening into a tropical depression as it arrives in southwestern Yunnan on Tuesday.
The storm is now moving 30 kilometers per hour (19 miles per hour) toward the coast of western Guangdong, mainland China, according to the HKO.
China and the Philippines agreed to postpone a visit by Chinese foreign minister Wang Yi that was to start on Sunday due to the typhoon's onslaught.
However, after striking Philippines, it is expected to weaken and will cross over to China Sea as a Cat 3 Typhoon.
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