Cyber attacks that caused a wave of Web site outages in the US and South Korea used 86 IP addresses in 16 countries, South Korea's spy agency told lawmakers Friday, amid suspicions North Korea was behind the effort.

The countries include South Korea, the United States, Japan and Guatemala, Chung Chin-sup, a member of the parliamentary intelligence committee, told reporters.

He spoke after being briefed by the National Intelligence Service, or NIS, on preliminary investigations of the IP addresses - the Internet equivalent of a street address or phone number.

The assaults on Web sites in the US and South Korea have been described as so-called denial of service attacks in which floods of computers try to connect to a single site at the same time, overwhelming the server.

The NIS also briefed lawmakers on circumstantial and technical reasons for believing that North Korea could be behind the attacks, Chung said without elaborating.

But the spy agency cautioned it was too early to conclude that North Korea was responsible as the investigations were still under way, according to Park Young-sun, another member of the intelligence committee.

"So far, North Korea was not included among the 16 countries' IP addresses," she told reporters.

US authorities also eyed North Korea as the origin of the trouble, though they warned it would be difficult to identify the attackers quickly.

Three US officials said this week while Internet addresses have been traced to North Korea, that does not necessarily mean the attack involved Kim Jong Il's government in Pyongyang. They spoke on condition of anonymity because they were not authorized to speak publicly on the matter.

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