In December 2010, a British ship (yacht) attempting to refuel in Massawa was detained by Eritrean authorities, and its crew of four has not been released. There are reports of additional vessels with nationals from other countries being detained for up to several months. In nearly all cases, the Eritrean government has neither given a reason for detention, nor granted consular access. The port of Assab is closed to private marine vessels.
US Travel warning - HERE
This relates to a recent report that a yacht with British crew (4) were arrested when attempting to refuel in Massawa towards the end of Dec '10 and have not been allowed consular access. Also, 4 German crew on a German yacht were arrested and held.