Two motorists have been seriously injured in a five vehicle crash involving two caravans on the Bruce Highway, north of Brisbane.

Five vehicles, including two caravans, have crashed on the Bruce Highway north of Brisbane, leaving two people seriously injured.

The pile-up happened near the Pine Rivers Bridge at Bald Hills about 10.40am (AEST).

All southbound lanes on the highway are closed, with traffic being diverted at North Lakes.

Police are also advising motorists heading north to maintain their speed on the highway to avoid causing further delays.