A ban on mining activity and exports in the east of Democratic Republic of Congo has left millions of dollars' worth of tin ore stuck in the conflict-strewn zone and put thousands of people out of work.

Rising insecurity in Congo's eastern Walikale district, home to most of the country's cassiterite - tin ore - and where more than 300 rapes took place in a rebel attack last month, prompted the government on September 11 to ban mining in North Kivu, South Kivu and Maniema provinces.

Emmanuel Ndimubanzi, head of the mining division of North Kivu, where the industry makes up 90% of provincial government receipts and which is the source of most of Congo's cassiterite, said more than 50 000 people were affected.

"We usually export $10-million a month in value, but this has come to a halt," Ndimubanzi told Reuters. "Trade has slowed down ... and mining planes have stopped, so provinces are no longer being supplied with food and goods."

Minerals Supply Africa (MSA), which buys from nearly half the middlemen in the province and exports 20 containers a month, much of it to Malaysia Smelting Corporation, also said the halt had put its business in doubt and thousands out of work.

"My credit lines are frozen, and I won't be able to make the money back even after the ban is lifted," David Bensusan of MSA told Reuters by telephone, adding he had $4-million worth of cassiterite tied up in containers unable to move due to the ban.

"We've got 40 tons of metal out there sitting in a warehouse in the bush worth $300 000, which isn't making me comfortable," said James Tidmarsh of exporter Tengen Metals.

Supply problems, mostly in Indonesia and China, have lifted the price of tin on world markets steadily since June, from $15 000 a ton to more than $24 000 this week, close to all-time highs.

"Congo's ban is a significant factor in the mix," said Peter Kettle, a market analyst at tin industry lobby ITRI.

Congo's expected 14 000 tons will make up about 5% of world production this year.

BAN RISKS SMUGGLING, INSECURITY

Around five-million people have been killed in the central African state since the start of a 1998 to 2003 war, and the government and UN forces are struggling to uproot various rebel groups still active in the east.

The surprise ban requires agents to present credentials and show the source of their funding to the government in an effort to "re-establish (the state's) authority over the land".

But detractors are concerned it will lead to a rise in smuggling and fail to reduce widespread insecurity and tackle the true control of mines by what the Ministry of Mines described as "mafia-like groups", which President Joseph Kabila blasted on launching the ban.

"This ban just came falling out of the sky - from the president - with no warning, and no one dares to go to the sky for clarification," said a western donor. "It's already damaging the economy in the east so badly we are considering humanitarian aid."

Gregory Mthembu-Salter, consultant to a United Nations panel of experts, said tin mines previously run by rebels have mostly been taken over by the army.

Minister of Mines Martin Kabwelulu told Reuters, "We know that there are officials who are engaging in illicit activities; we are putting them under observation."

Many expect the ban to be lifted by October 15, but Kabwelulu said no date has yet been fixed.