Increases in coal exports last week created a backlog which resulted in 61 vessels - the highest since mid-2007, queuing to load coal at Australia's eastern port of Newcastle.

The world's biggest export port for coal experienced a 3.6% increase in coal shipments to up to 2.11 million metric tonnes last week, according to Newcastle Port Corporation.

The financial year, which ends in June, may have prompted some producers to sell more shipments of coal to improve their books, increasing the load on the port, sources told Reuters.

However, the producers attributed the spike in waiting time to the introduction of a new satellite tracking system.

The port's tracking system, designed to coordinate ship arrivals, cut waiting times, reduce costs and improve safety, was initiated after Pasha Bulker, a bulk carrier, ran aground at Nobbys Beach, south of Newcastle harbour in June 2007.

The port ships mostly thermal coal used in power plants.

The queue has since eased to 53 at the start of this week.