DUBAI - Cyber attackers have targeted Iranian infrastructure and communications companies, disrupting the Internet across the country, a state official was quoted as saying on Wednesday.

Iran, the world's No. 5 oil exporter, has tightened cyber security since its uranium enrichment centrifuges were hit in 2010 by the Stuxnet computer worm, which Tehran believes was planted by arch-adversaries Israel or the United States.

"Yesterday we had a heavy attack against the country's infrastructure and communications companies which has forced us to limit the Internet," Mehdi Akhavan Behabadi, secretary of the High Council of Cyberspace, told the Iranian Labour News Agency.

"Presently we have constant cyber attacks in the country. Yesterday an attack with a traffic of several gigabytes hit the Internet infrastructure, which caused an unwanted slowness in the country's Internet," he said.

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