Earlier on Wednesday, the government had said it was not necessary for schools to close. But hours later, at around 10.30pm, Health Secretary York Chow ordered all primary schools and kindergartens to close for two weeks starting yesterday.

Explaining his decision at a press conference a day later, Mr Chow said he acted quickly because 'when you wait until you have all the data, it is too late'.

He apologised yesterday for giving such short notice to teachers and parents.

The schools had been expected to start their Easter Holiday in a little over a week, though the date varies with each school.

Mr Chow said bringing the holiday forward would help reduce cross infection among schoolchildren and calm public fears.

Schools will be closed for two weeks until March 28 - twice the incubation period for the virus, he said.

Health experts, teachers and parents generally support the decision to close the schools early, but parents were angry over how the government handled the closures, particularly the late notice.

Mr Leung Kee Cheong, principal of the Fresh Fish Traders School, said the late decision meant staff could not contact parents before they arrived at school yesterday.

'But if this is for the safety of students, this is unavoidable,' he was quoted as saying by South China Morning Post.

Mr Li Kin Fai, a teacher at Aplichau Kaifong Primary School, said: 'If they had informed us earlier - before 6pm - we could have adopted emergency plans and maybe called parents about the suspension.'

At the Cho Yiu Catholic Primary School, nine students arrived early yesterday.

School staff took their temperature and gave them masks. The students read picture books instead of attending class.

'I am worried that I will get infected. Many classmates have been infected with the flu. I am afraid,' said nine-year-old Winnie Ting, who was already wearing a mask before arriving at school.

An angry mother told local RTHK radio: 'People have to go to work. We cannot just suddenly take a day off or find someone to look after our kids.

'They should give us one or two days' notice so people can be more prepared.'

ASSOCIATED PRESS