An unknown computer intruder forced the Pentagon to cut links between an unclassified military network and a nationwide academic and corporate network for several days, The New York Times reported Thursday.

The academic and corporate computer network, known as Arpanet, was the same one crippled last month by a computer virus, which is being investigated by a federal grand jury in Syracuse.Officials said Wednesday the Defense Department move was due to technical difficulties.

However, several unidentified computer security experts told the Times that Pentagon officials had informed them the network connection was severed after the intruder illegally gained entry recently to several computers operated by defense contractors and the military.

The experts said they believed the Pentagon broke the connection, which permits military and academic researchers to exchange information, while it tried to eliminate a security flaw in the military network, the Times said.

An unidentified Defense Communication Agency spokesman said in a statement that the links between the two networks were cut at 10 p.m. Monday, and were to be restored Thursday.

The Defense Department apparently acted after a computer at the Mitre Corp., a Bedford, Mass., think tank with several military contracts, was illegally entered several times over the past month, The Times said.

Officials at several universities in the United States and Canada said the intruder used their computers to reach Mitre's.

Mitre spokeswoman Marcia Cohen said one of the company's computers had been entered, but said the computers involved had not handled any classified or sensitive information.