KHARTOUM - Three Sudanese soldiers were killed when government forces attacked a refugee camp in Darfur, the second assault reported on a shelter for displaced people in less than a week, the United Nations said on Monday.

The fighting, at Hamidiya camp near the western town of Zalengei, was the latest in a series of clashes just days before planned peace talks between Sudan's government and rebel groups.

No one from the Sudanese armed forces was immediately available for comment.

France's secretary of state for human rights and foreign affairs, Rama Yade, speaking at the start of a two-day visit to Khartoum and Darfur, said on Monday security in Sudan's remote west was worsening.

The U.N. mission in Sudan said there had been reports of three killings after Sudanese troops surrounded Hamidiya Camp and started shooting into the settlement on Saturday.

A U.N. spokeswoman said the troops moved in following reports that displaced people had killed a government intelligence officer inside the camp earlier the same day.

"SAF (Sudan Armed Forces) soldiers tried to enter the camp twice. Initial reports indicate that SAF suffered three casualties," the spokeswoman said. "Some IDPs (internally displaced people) have reportedly left the camp in fear of a further attack."

A few days earlier, residents in Kalma camp outside Nyala, the capital of South Darfur, reported a series of raids by government-backed militias. The African Union later confirmed that armed assailants had attacked the camp, killing several people.

The state-controlled Sudanese Media Centre on Sunday reported 10 per cent of Kalma's population had fled since the violence, which it blamed on clashes between tribal groups in the settlement. It made no mention of militias.

The government denies arming militias and tribal factions in Darfur, although it has raided camps in the past in search of rebel strongholds.

International experts say 200,000 people have been killed in more than four years of fighting, raping and looting in Darfur and more than 2.5 million have been driven from their homes to seek refuge in camps such as Kalma and Hamidiya.

Khartoum says the figures have been exaggerated by the media and campaign groups.

France's Yade told reporters on Monday she had delivered a letter from French President Nicolas Sarkozy to Sudanese President Omar Hassan al-Bashir, setting out concerns about the worsening situation in Darfur.

"There is still immense suffering," she said. "We know from UNICEF that 35 children still die every day. We know that women are still raped. We strongly condemn those responsible for these serious crimes, which are crimes against humanity and war crimes."

Yade said the French government would keep up efforts to persuade defiant Darfur rebel leader Abdel Wahed Mohamed Ahmed el-Nur to leave Paris and attend peace talks in Libya.

Nur, the founder of the Sudan Liberation Army, has refused to join other insurgent groups in Libya, demanding a series of concessions from the government ahead of negotiations.

"The Libyan negations will begin on 27th October," said Yade. "We will do all we can to persuade him to join those negotiations in the run up to that date," she said.

Yade added France was ready to support a 26,000-strong force of U.N./African Union peace keepers in the region "if it proves necessary". The force is due to replace a hard-pressed body of 7,000 African Union peacekeepers from Jan. 1.

Concerns have already been raised about whether it will be ready in time. The U.N. on Sunday said it was lobbying countries to provide 24 transport and attack helicopters.