Zim is the latest boxship company caught in the sights of an alleged patent troll, while two of its competitors have returned fire in their legal battles.

Transcend Shipping Systems sued the New York-listed, Israel-based containership operator on 30 March, accusing it of infringing five of its patents related to its container tracking system.

"The Transcend patents each include numerous claims defining distinct inventions," read the complaint, filed in the US federal court for the Eastern District of Texas.