Singapore's Prime Minister Lee Hsien Loong called Thursday on members of the Association of Southeast Asian Nations (Asean) to strengthen their cyber security systems, media reports said.
He was speaking at the opening ceremony of a meeting in Singapore of Asean telecommunications and information technology ministers.
"We must not condone such malicious and harmful behaviour," the Straits Times quoted him as saying.
"We must strengthen our defences and cooperate to deal with these common threats."
Lee was speaking after a spate of recent attacks targeting Singapore, Thailand and the Philippines.
The official websites of Lee and Singapore's president were hacked last week, apparently by members of the shadowy activist group Anonymous.
In Thailand, a total of 2,960 local websites were hacked from September 2012 to last January, of which 1,250 were government sites, according to Prinya Hom-anake, founder of ACIS Professional Centre, an IT security training company.
In May 2013, the Office of the Prime Minister's website was hacked, with messages and a photograph deriding Yingluck Shinawatra posted on its homepage. In September, the Education Ministry's website was hacked and messages in Thai and English saying that the ministry should have no right to control teenagers were posted on the site.
Singapore's Prime Minister Lee Hsien Loong (Bloomberg Photo)