(Adds British travel warning, JEM comments)

By Opheera McDoom

KHARTOUM, May 9 (Reuters) - Sudan's army has stepped up security in Khartoum, saying it has intelligence that a heavily armed convoy of Darfur rebels has advanced to the neighbouring Kordofan province and is planning an attack.

But the rebel Justice and Equality Movement denied any move on Sudan's capital and accused the government of trying to distract attention from recent bombing raids on Darfur that have brought international condemnation.

Heavy security operations began late on Thursday in Khartoum. Bridges were closed and checkpoints set up in the streets, forcing many people to stay at home.

"There were some forces from the Justice and Equality Movement who crossed from Chad through Darfur to Kordofan where they were aiming to cause destruction in Khartoum," an army spokesman said. "The army is on a heightened state of alert."

An advance to Kordofan would be the closest the Darfur rebels have come to Khartoum in years. North Kordofan borders Khartoum state and almost abuts the capital itself.

The army spokesman said the rebels had halted their advance and remained in Kordofan after they found out forces in Khartoum had been alerted. The state news agency quoted an army statement as saying troops were on alert in other cities too.

There was no independent confirmation of the rebel advance in the vast country of deserts and scrub, where military movements can be hard to track. And reports were conflicting from JEM.

A senior JEM official in Britain al-Tahir al-Feki said JEM did have forces in Kordofan but were not planning to attack Khartoum. But the JEM humanitarian coordinator for West Darfur, Sheikh el-Din Mahin, told Reuters from Darfur JEM troops were on their way to the capital. "We have forces close to Khartoum and we can hit Khartoum at any time," he said.

TRAVEL WARNING

Senior JEM field commander phones were off on Friday, which Mahin said was because of the operation. Britain's foreign office issued a travel advisory warning any nationals against travel to Kordofan.

"You should be aware of the risk of rebel attacks spreading outside Darfur and exercise extreme caution at all times," it said.

Two senior diplomats in Khartoum told Reuters they had been warned by the Sudanese foreign ministry of an imminent attack on Khartoum and had that the international community had raised all security measures.

"After they have been bombing Darfur and committed a massacre in Shegeg Karo ... everybody is condemning them, so the best way for them to divert attention away is to do this," JEM spokesman Ahmed Hussein Adam said from London.

Sudanese planes last Sunday bombed a school and market in Shegeg Karo killing 12 people including 6 children, witnesses said. The bombing was condemned internationally.

Sudan has falsely accused political opponents of planning coups in the past.

The increasing violence in Darfur has added to doubts over prospects for a peace deal. The five-year-old conflict has driven 2.5 million from their homes with international experts estimating some 200,000 have died. Khartoum says only 10,000 people have been killed.

The world's largest humanitarian operation provides aid to two-thirds of the population of Darfur's west, which borders Chad. Darfuri rebels took up arms in 2003, accusing the government of neglect and marginalisation.

(Editing by Matthew Tostevin)

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