Those on board the Free Gaza Movement's 'Spirit of Humanity' include Nobel laureate Mairead Maguire and former U.S. Congresswoman Cynthia McKinney, as well as a number of UK nationals.
The boat, which was searched and received security clearnace before leaving Cyprus, has apparently been turned towards Israel. Free Gaza claim the workers have been 'kidnapped'.
Cynthia McKinney said: "This is an outrageous violation of international law against us. Our boat was not in Israeli waters, and we were on a human rights mission to the Gaza Strip.
"President Obama just told Israel to let in humanitarian and reconstruction supplies, and that’s exactly what we tried to do. We're asking the international community to demand our release so we can resume our journey."
Palestine Solidarity Campaign have sent out the following message, asking that it be sent to Foreign Secretary David Miliband (firstname.lastname@example.org) and a copy to your MP.
(Those outside the UK should do the same but with your respective representatives).
Dear Foreign Secretary,
I was extremely concerned to hear the news today that the Israeli Navy illegally intercepted and boarded the Free Gaza ship 'Spirit of Humanity', whilst it was in international waters. It appears they have kidnapped the 21 human rights workers from 11 countries, including UK citizens Ishmahil Blagrove, Alex Harrison, Denis Healey, Fathi Jaouadi, Theresa McDermott and Adnan Mormesh, and taken the boat to an Israeli port.
The boat holds medicine, toys, and other much needed humanitarian relief for the Palestinians living in Gaza under siege. Its cargo was searched and it received a security clearance by Cypriot Port Authorities before departure.
As the International Committee of the Red Cross said in their report released yesterday, the Palestinians living in Gaza are "trapped in despair." Thousands of Gazans whose homes were destroyed earlier during Israel's December/January massacre are still without shelter despite pledges of almost $4.5 billion in aid, because Israel refuses to allow cement and other building material into the Gaza Strip. The report also notes that hospitals are struggling to meet the needs of their patients due to Israel's disruption of medical supplies.
I urge you to insist that the Israeli Government immediately release the Spirit of Humanity and all its passengers, and take all the necessary steps to ensure it can complete its humanitarian mission in safety. I also urge you to act to ensure that the Israeli government does not commit any further acts of piracy and kidnapping of boats and their crew in international waters.
Please note - you would be better off using this as a template of sorts and rewording any actual message. MPs tend to scoff at copy and paste jobs.