A packoff for hanging a liner string from a tubular string cemented in a wellbore includes: a tubular body having an outer groove and an inner groove; an inner seal assembly disposed in the inner groove; an outer seal assembly disposed in the outer groove; a cap connected to an upper end of the body for retaining the seal assemblies; a plurality dogs disposed in respective openings formed through a wall of the body; and a lock sleeve. The lock sleeve is: disposed in the body, longitudinally movable relative to the body, and has a cam profile formed in an outer surface thereof for extending the dogs.