Russia, the world's largest oil producer, faces domestic fuel shortages after authorities restricted the transport of crude oil by rail, forcing several refiners to cut production, industry and market sources said

The move has taken thousands of tonnes of oil products of the market in recent days, threatening a repeat of last year's fuel shortages following Russian leader Vladimir Putin's order to oil companies to curb pump prices.

However, it is unlikely to dent crude exports, as Russia uses pipelines as its main method of transporting oil abroad.

Russia's transportation safety watchdog has banned the use of rail wagons designed to handle light oil products to ship crude and heavy fuel oil, following several rail accidents.

That has cut the number of wagons in operation, several oil refineries said, curbing supplies and forcing them to cut runs.

Mid-size producer Orsknefteorgsintez, said its heavy oil shipments slumped by almost a half. "We will only be able to function for 10 days in this mode," a company representative said. "We hope the situation will be resolved by then."

The Khabarovsk refinery, operated by Alliance , said on Wednesday it reduced throughput by half following the ban.

"As a result (of the decision) oil refinery declined from 11,200-11,300 tons per day to 5,100," a spokesman said.

Representatives of several other refineries have expressed concerns over the ban, but would not comment on the record.

A spokesman for Rosneft, Russia's largest crude producer, said that the company has written to Transportation Minister Igor Levitin asking him to postpone the ban until Aug. 1.

The ban was set on May 5, according to a document posted on the watchdog's website www.rostransnadzor.ru.

The spokesman declined to comment on possible refinery problems.