At least a dozen international aid volunteers are on board a boat off the coast of Libya, where they are allegedly being held captive by the boat’s captain, according to the British government.Seven British members of an aid convoy to Gaza are being held captive in the Libyan sea, aboard a Greek boat, UK Foreign Office spokesman confirmed Thursday.

The British volunteers, along with survivors of the Israeli attack on the Mavi Marmara aid ship in May, are among a group reportedly trapped in the Mediterranean on Strofades IV, a Greek cargo vessel due to deliver aid to Gaza.

The UK spokesman did not confirm initial reports that the Strofades IV was being chased by Libyan navy ships and fighter jets.

The volunteers from Road to Hope, a humanitarian group attempting to deliver help to Gazans, are allegedly being held by the ship’s Greek captain due to a dispute over money.

Ellie Merton, London liaison for the convoy, stated: ‘As far as I know, the boat owner became really aggressive over a payment for something…[and he] drove the boat away from the pier really fast.

‘The [vessel] was still attached to the quayside, and as he drove he yanked the ropes off, there were bits of concrete flying everywhere. We have lost telephone contact with those who are still on the ship against their will – without any paperwork, passports or authority to leave Libya, possessions or, when we last heard, food or water. We’re extremely concerned.’

As well as the British volunteers, two Irish volunteers, one Algerian volunteer and three Libyan officials are on the ship. Among them are Ken O’Keefe, a former U.S. marine, and British citizen Tauqir Sharif, who were both on board of the Mavi Marmara, which was raided by Israeli forces last May, resulting in the deaths of nine activists.

British Foreign Office diplomats are liaising with the Libyan and Greek authorities, and have urged a ‘safe’ resolution to the incident.