SINGAPORE, Nov. 20 (Xinhua) -- The websites of 13 schools in Singapore were reported defaced on Wednesday afternoon.

The websites of all the 13 schools were on a single server that was affected, local broadcaster Channel NewsAsia said.

The Ministry of Education has referred the matter to the police for investigation and it is working to restore the affected websites.

Separately, the Singapore Art Museum said the contact information of some 4,000 people kept in a data file on its website has been illegally published and uploaded to a server in New Zealand.

The museum said the Infocomm Development Authority of Singapore alerted it of the situation on Nov. 5. Upon receiving the alert, the museum immediately removed the data file from its website and filed a police report, it said.

The incident has not been classified as online hacking, but local daily said the police are not ruling out the possibility.

It was not clear if the incidents are related to earlier incidents targeting the websites of local authorities including the Prime Minister's Office and the Istana, the presidential palace of Singapore.

The attempted attacks on the websites of the Prime Minister's Office and the Istana earlier this month came after alleged members of international hackers collective Anonymous threatened attacks on local information infrastructure in early November.

Minister for Law and Foreign Affairs K Shanmugam said on Wednesday that the government takes cyber hacking very seriously because of Singapore's dependence on information technology.

People's jobs could be affected if hackers attacked the commercial sector and took down banking and financial systems, the minister said, citing the recent case of personal data being compromised when the Singapore Art Museum website was affected.

Cyber attacks could yield other consequences, for example, if medical records of hospital patients were stolen, he said.

He said the government and the people are intricately linked, so an attack on the state will have consequences on both parties.

"Hacking in real terms is nothing short of terrorism," he said.