Four retired marines have been held captive for more than eight weeks in the Horn of Africa after a gun battle while they were escorting a merchant ship through waters threatened by pirates.

The Independent has learnt that the group are accused of spying after being arrested by a naval vessel from Eritrea as they guarded the ship in the Indian Ocean. A dispute about their paperwork escalated and threats were followed by shots being exchanged. Two of the ex-Marines tried to escape in a skiff but were seized after a chase. They were, it is claimed, kept on an offshore island without food or water for more than a day before being taken back to a port city on the mainland for incarceration.

British diplomatic sources say that Eritrean authorities have refused access to the four captives despite repeated requests made to see them in the Eritrean capital, Asmara, as well as representations made at the UN forum in New York, and the Eritrean legations in Berlin and the Sudanese capital, Khartoum.

The men are said to be held under extremely harsh conditions in jail and two of them have become ill. It is alleged that Eritrean officials have warned the men that there is no prospect of early release and they can expect to face charges of espionage.

A Foreign Office spokeswoman said last night: “We can confirm that four British nationals are detained in Eritrea and we are seeking access to them as a matter of some urgency.”

Relations between Eritrea and Western states are fractious with the government in Asmara accused of helping Islamist rebels in Somalia and undermining the government in Ethiopia. A Whitehall official said: “Eritrea and the UK have not really had much contact historically and as a result there isn’t much of a mechanism in place for dealing with something like this. Eight weeks is a long time for holding foreign nationals and this is obviously of deep concern.”

The group of former British military personnel is believed to have connections with the security company PVI. Last night a representative of the company said that none of its employees were under arrest.

Foreign states who police the Horn of Africa with naval ships have started taking a more aggressive stance towards piracy with raiders being tried in Western Europe and Kenya. Speaking at an anti-piracy conference in London, the United Nations Secretary-General, Ban Ki-Moon, said that piracy in the area is “one of the most pressing problems facing the international community and completely unacceptable”.

A number of alleged spokesmen for pirate groups in Somalia have threatened that retribution would be taken against any persecution by Western powers. Major General Julian Thompson, a former commandant of the Royal Marines, said: “There is an ongoing debate about whether security personnel operating in these areas should be armed. The other factor one needs to consider is whether these Eritrean naval personnel are in cahoots with pirates. If that is the case we have a hostage situation and a variety of options have to be looked at.”

(Source: The Independent)