Relatives of Scots activists who were on board an aid convoy when it was stormed by Israeli soldiers are still waiting to hear if they are safe.
Five Scottish volunteers are thought to have been with the flotilla when it was intercepted in international waters as it headed towards Gaza.
At least ten people died when the commandos opened fire.
The UK foreign office said it was not aware of any British nationals being killed in the raid.
However, one Briton was said to have been injured in clashes between the Israeli forces and some of the 500 people on the largest ship in the six-strong aid convoy.
Among the Scots with the flotilla at the time was Theresa McDermott, from Edinburgh, as well as journalist Hassan Ghani and IT professional Hasan Nowarah, both from Glasgow, and Dundee-based estate agent Ali El-Awaisi.
Winnie Chambers, the sister of 43-year-old postal worker Ms McDermott, told BBC Radio Good Morning Scotland that she had not heard from her sister since the raid, which happened in the early hours of Monday morning.
She said: "The last we heard from her officially was about three o'clock in the morning. She had one of these sport GPS devices and it sent a message saying they had been contacted by the Israelis and we weren't to worry and then we heard nothing else.
"We have obviously seen all that violence on the Turkish ship yesterday was just shocking and appalling.
"There's been no report that the other trips were similarly treated but we don't know. Until we hear something from the ship, from the foreign office, from somebody, we are completely beside ourselves with worry."
The Israeli government has claimed its forces were shot at and attacked with weapons when they boarded the lead ship, the Mavi Marmara.
Dr Khalid El-Awaisi told Good Morning Scotland he did not know if his 22-year-old brother Ali El-Awaisi was alive or dead.
But he said: "There were no weapons on that ship.
"My brother was telling me as they were leaving the port of Antalya they were security checked like you would be at any port. Not even a single Swiss knife was found on that ship."
The flotilla had left the coast of Cyprus on Sunday with the intention of carrying 10,000 tonnes of aid to Gaza, despite Israel warning the boats would be allowed to reach their destination.
A blockade was imposed by the Israelis after the Islamist movement Hamas took power in Gaza in 2007.
Scotland's Deputy First Minister Nicola Sturgeon said on Monday that Israel's actions had been "rightly condemned around the world" and called for the blockade of Gaza to be lifted.
Demonstrations against Israel's actions were held in cities across Scotland on Monday afternoon.