A commercial oil tanker that was seized and returned by US forces after it loaded crude at a Libya port held by anti-government rebels, has docked back in the capital Tripoli, a Reuters witness said on Sunday.

The Morning Glory tanker was due to arrive later at Libya's Zawiya port, where its cargo of crude is to be feed to the Zawiya refinery.

US special forces seized the tanker a week ago off Cyprus, days after it left Libya with a cargo of crude from Es Sider port, which is controlled by rebels who demand more autonomy and oil wealth in defiance of the central government.