Foreign Secretary William Hague has ordered UK ambassadors around the world to raise concerns about the detention of four British men in Eritrea.
The captives are reported to be former Royal Marines working for a private security company who were seized while escorting a merchant ship through the piracy-plagued seas around the Horn of Africa.
The Foreign Office said it was “deeply concerned” that the Eritrean authorities were continuing to refuse to let British officials see the men.
Africa Minister Henry Bellingham summoned the Eritrean ambassador in London to the Foreign Office on January 17 and 20 to repeat requests for access to the four captives.
And on Monday Mr Hague instructed the British ambassadors in New York, Brussels, Khartoum, Tripoli, Nairobi and Beijing to raise the issue as a matter of priority with their local Eritrean counterparts.
The Britons have been held in harsh conditions for more than eight weeks on suspicion of spying after they were arrested by the Eritrean navy following an exchange of shots, The Independent reported.
A Foreign Office spokeswoman said: “We can confirm the detention of four British nationals in Eritrea. We have been been urgently seeking consular access since we became aware of their detention.
“We are deeply concerned at the failure of the Eritrean authorities to allow us to speak to or visit the men.”