Clues gathered by investigating teams in Karnataka over Wednesday's terror attack on the prestigious Indian Institute of Science have led them to suspect involvement of Pakistan's ISI trained terrorists, a police source said on Thursday.

"The inputs indicate the involvement of ISI trained terrorists," a highly placed source, speaking on condition of anonymity, told PTI.

The police suspect it was a four-member gang that executed the attack, leaving a retired professor of Indian Institute of Technology, Delhi, dead and four others wounded.

The city police believe that the attackers did not use any vehicle, but the source maintained that the gang did use a car and managed to flee in it.

The source said the investigating teams did not also rule out the role of underworld don Abu Salem's [Images] associates in the attack. Abu Salem, a key accused in the Mumbai serial blasts, has been brought here to undergo polygraph and brain mapping tests.

No terrorist outfit has claimed responsibility for the attack. Chief Minister N Dharam Singh has said police have obtained certain "clues" and hoped to zero in on the culprits soon.

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