The service, at a Russian Orthodox Church, follows the discovery of four bodies on the outskirts of the capital on Friday.

Allan Little: "The bodies will be returned as soon as possible"

Chechen presidential spokesman Mairbek Vachagaev was quoted by the Itar-Tass news agency as saying the bodies would be returned to Britain within days.

A spokesman for the UK Foreign Office said he could not confirm the report.

"There are so many rumours flying about that we cannot comment on anything until we have checked the reports out ourselves," he said.

The four victims were installing a mobile phone network

The decapitated heads of the four men - Darren Hickey, Peter Kennedy, Rudolph Petschi and Stanley Shaw - were discovered by a roadside on 8 December.

One unconfirmed report said they had been killed after a bungled attempt to rescue them. Another report said they were murdered after a dispute between rival kidnap gangs over the share of a ransom from another kidnap.

The Chechen authorities say they have arrested a man, named as Abti Abitayev, whom they describe as the mastermind behind the abduction and that information he is supplying should lead to the arrest of other members of the kidnap gang.

But the BBC correspondent in Moscow, Allan Little says that clamping down on one gang is only part of an uphill battle in a hopelessly lawless area.

Kidnapping commonplace

The four men - employed by the UK firm Granger Telecom - were installing a mobile phone network for the Chechen government. A gang of 20 gunmen abducted them in October after a fierce battle in Grozny.

The UK Government described the murders as "repugnant."

Law and order in Chechnya has virtually broken down and foreigners working there have become lucrative targets for kidnap gangs.

However, while kidnapping is commonplace and hundreds locals have been killed, they were the first foreign hostages to lose their lives.

Other kidnap victim released

In another development, a Russian police officer seized in June is reported to have been released in exchange for a Chechen prisoner in Russia.

Sergei Khalansky's kidnappers had demanded a large ransom. His release was negotiated by the governor of the Siberian region of Krasnoyarsk, Alexander Lebed.