Freight traders are hiring record numbers of iron-ore carriers in the spot market as mainland steel production expands at the fastest pace in three years, spurring the biggest rally in shipping rates since 2009.

One time charters to haul the commodity on capesizes, the largest ore carriers, rose 51% to 124 last month from August, according to data compiled by Morgan Stanley. More than 90% are bound for China and the ore they carry would make enough steel to build about 150 Golden Gate Bridges. The surge means more demand for Nippon Yusen KK and Mitsui OSK Lines, which are based in Tokyo and control the biggest fleets.

The jump in chartering reflects average monthly mainland steel output that has been about 10 per cent higher this year, reducing ore stockpiles to the lowest for this time of year since 2007.

Mainland imports of the raw material hit a record high last month, trimming the fleet's biggest capacity glut in three decades and spurring an almost sevenfold surge in rates since January 2 that has seen shipowners make money for the first time in almost two years.

Mr Eirik Haavaldsen an analyst at Oslo-based Pareto Securities said that "Rates have moved quicker than even the most optimistic forecasters had hoped for only a few months back. We have really seen a restocking commencing."

Daily rates for capesizes, each hauling about 160,000 tonnes, jumped to a 34 month high of USD 42,211 on September 25, according to the Baltic Exchange, which publishes shipping costs for more than 50 marine routes. They were at USD 31,545 on Monday. Freight swaps, traded by brokers and used to bet on future rates, anticipate a fourth-quarter average of USD 28,500, the most since 2011. The 300-metre carriers need about USD 14,500 to break even, according to RS Platou Markets, an investment bank in Oslo.