May 5 (Bloomberg) -- South Africa's Richards Bay Coal Terminal, the world's biggest coal-export facility, shipped 4.6 percent less of the fuel in April after heavy rain cut output from BHP Billiton Ltd., Anglo American Plc and other producers.

The terminal shipped 5.97 million metric tons of coal in the month, RBCT said today in an e-mailed statement. It exported 6.26 million tons a year earlier and 4.62 million tons in March this year.

Coal from Richards Bay climbed to a record earlier this year as transport bottlenecks and rain in Australia, the world's biggest exporter of the fuel used in power plants, spurred Asian customers to seek alternative sources. It traded at a six-week high of $112.15 a ton as of April 25, according to McCloskey Group Ltd.

The port received 4.64 million tons of coal by rail in the month, the lowest level in at least 17 months, as 572 trains arrived. That compares with deliveries of 5.53 million tons in March. Sixty-eight ships were loaded in April.

Sandile Simelane, a spokesman for Transnet Freight Rail, which operates the rail line, said he couldn't comment because the company is in a ``closed'' period before the release of its annual report. He didn't know when the annual report will be released. Transnet Freight Rail is owned by state-owned transport company Transnet Ltd.

Stocks fell to 2.42 million tons at the end of April, their lowest this year, from 3.67 million tons the month earlier, the port said.

Richards Bay Coal is owned by South Africa's biggest coal exporters, including Anglo, BHP and Xstrata Plc. While it is the world's biggest coal-export terminal, Australia's Newcastle port ships more of the fuel from two terminals.

At the current average monthly rate, Richards Bay will ship 57.74 million tons of coal this year compared with export capacity of 76 million tons. Smaller volumes of South African coal are exported from Durban as well as from Maputo in neighboring Mozambique.

South Africa is the biggest supplier of coal to European power plants.