China's most popular search engine, Baidu, is accusing its US-based domain name registry of negligence in a lawsuit over a hacking attack that temporarily blocked access to the site last week.

Baidu said it has filed suit against in a New York court, seeking unspecified damages.

Hackers blocked access to Baidu on 12 January by steering traffic to a website where a group reportedly calling itself the "Iranian Cyber Army" claimed responsibility. There was no evidence the hackers were linked to Iran.

"Due to US domain name registry service's gross negligence, Baidu's domain name domain name resolution was illegally and maliciously altered," the Beijing-based company said in a statement.

Resolution refers to the process that matches a website address written in words to the string of numbers that computers recognise as its place on the internet. Baidu gave no details of what it accuses the registry of doing wrong. called the lawsuit "completely without merit."

" takes cyber-terrorism very seriously and we are working closely with federal law enforcement officials who are investigating this crime as well as the recent similar attacks on Twitter and Google," the said company spokeswoman Alice McGillion in a prepared statement yesterday.

Baidu, pronounced "by-doo," has about 60 per cent of China's online search market, compared with about 35 per cent for US-based Google, which last week threatened to threat to shut down its search engine in China over online censorship and hacking.