"The former prime minister died at his home at around noon," the aide told Yonhap News Agency.
Lee served six terms as a lawmaker from 1981 to 2000 and as prime minister from 2000 to 2002 under then President Kim Dae-jung.
In 2002, he made an unsuccessful presidential bid with a pledge to eradicate regionalism and corruption.
In 2004, he was indicted without detention on charges of taking illegal political funds worth 200 million won (US$170,000) in cash from SK Group during the presidential election.
The Seoul Central District Court handed him a two-year suspended sentence and ordered him to pay 200 million won in restitution. (Yonhap)