KUALA LUMPUR, Sept 22 (AFP) - Malaysian police have detained a seventh associate of Anwar Ibrahim under the country's Internal Security Act following the arrest of the ousted deputy prime minister, a source said Tuesday.

The source, who asked not to be named, identified the seventh person as Kamaruddin Jaafar, a director of the Institute of Policy Studies, a think tank affiliated with Anwar.

The institute also has close ties with a think tank associated with Indonesian President B.J. Habibie, who is said to have telephoned Anwar shortly after his September 2 dismissal as deputy prime minister and finance minister.

Malaysia's internal security act allows police to detain suspects for an indefinite period without trial.

Police confirmed Monday thar two of Anwar's close allies in the youth wing of the ruling party and four leaders of a Moslem youth movement which Anwar once headed were also picked up under the draconian law.