The Foreign Office says Doug Scrafton is returning "for consultations."

A Foreign Office spokesman also confirmed that the five were now in Harare, Zimbabwe, after leaving the Congolese capital Kinshasa on Thursday night.

Arrangements were being made for their onward transport.

"We welcome the release of the detainees who are safe and well and on their way home," the spokesman said.

"There was no question of them having been spying.

"We take this incident extremely seriously and we are considering our response."

Stephanie Wolters reports: Immediate expulsion for "ill intentions"

The five were issued with expulsion orders by interior minister Gaetan Kakudji late on Wednesday. A US official was also ordered out of the country.

The group was arrested on Sunday near the international airport by soldiers manning roadblocks.

According to Congolese authorities, they were found carrying maps with strategic installations highlighted.

But the Foreign Office described their activity as part of contingency planning for the evacuation of about 200 British citizens living there.

Routine business

A spokesman said this was "routine business", carried out by embassies across the world. "It is nothing at all unusual," he said.

One of the Britons was named as Gregor Lusty, Third Secretary at the British Embassy in Kinshasa.

The names of the other Britons were not released but they were identified as a London-based consular official, two Ministry of Defence officials and a member of the embassy's security staff.

The two MoD men were thought to be officers from Britain's Rapid Reaction Force which would be responsible for moving British nationals from the Congo if they were considered to be in danger.

The American is believed to be a State Department official on secondment to the Foreign Office.

On Wednesday, Foreign Office minister Tony Lloyd phoned President Kabila to express British dismay over the incident.

Congolese Government forces are currently involved in a conflict with rebel troops seeking to overthrow President Kabila.

Last August, rebels came close to entering Kinshasa before being beaten back by government soldiers supported by troops from Zimbabwe and Angola.

Correspondents say the local authorities have accused the rebels of hiring foreign mercenaries and suspicions of foreigners have heightened in recent weeks.