UK restricts Eritrean diplomats
London - Britain said on Thursday it had restricted the movement of Eritrean diplomats in protest at being denied access to four Britons held in Eritrea.
The four men, who work for a company that provides security for ships in a region where piracy is rife, were detained last December after they docked at an Eritrean port to refuel.
Their employer, British-based Protection Vessels International, has said it believes their ship was intercepted by the Eritrean navy as it left the port, apparently because of confusion over payment for the fuel.
Britain said it had been denied consular access to the four men and Eritrea had rebuffed its attempts to discuss the issue.
"We are deeply concerned by the situation and have been left with no alternative than to take a more direct approach," Britain's foreign ministry said in statement.
The Foreign Office said it had barred Eritrean diplomats and visiting officials from travelling outside London without written permission.
British officials have also told the Eritrean ambassador that the collection of a tax levied by the country's government on its nationals living in Britain could be illegal and ordered it to stop collecting the tax.
"We continue to call on the Eritrean government to adhere to its obligations under the Vienna Convention on Consular Relations by allowing consular access to the four detainees," the Foreign Office said.
The British government warned Eritrea last month it would take "robust action" if it was not granted consular access to the four.
In April, Eritrean President Isaias Afwerki said the four Britons possessed large quantities of arms, but did not say whether they would be charged with any offence.
Eritrea is one of the world's most secretive nations and has frosty relations with a number of Western countries as well as most of its neighbours, having been involved in border disputes with Ethiopia and Djibouti.
Britain has in the past called for "punishment" of Asmara for its suspected support of Islamist insurgents in Somalia. The United Nations imposed sanctions on Eritrea in late 2009.