A Swiss firm has cancelled a 3000t cement order by activists involved in the aid flotilla for Gaza largely thwarted by the Greek authorities, Swedish activists said Wednesday.

In an email to the "Ship to Gaza Sweden" campaign dated Tuesday, Interbulk Trading cited the Greek foreign ministry ruling banning vessels bound for Gaza leaving its ports.

"Therefore, due to force majeure we cannot deliver the cement and we are going to send back to your account the €25,200 we received as an advance payment," the email from a division of Italy’s Italcementi said.

"Ship to Gaza Sweden" described the Greek’s ban as "deeply disturbing and completely reprehensible in democratic constitutional states.

"It is difficult to perceive the Greek government’s actions as anything but an assault on the European civil society and business," it added.

Officials in Athens say they imposed the ban for the "safety" of the activists on board in the wake of last year’s bloody showdown.