The “Dignite al Karama” is so far the only boat in a planned flotilla organised by pro-Palestinian activists to set sail from Greece, after the authorities there blocked other vessels from leaving the port of Athens, Piraeus.

The 19-metre (63-foot) yacht had nine passengers aboard and expected to be “off Gaza within an day or two,” said a statement from the French Boat to Gaza campaign. 

“They are going to break the blockade in the name of the Freedom Flotilla, in the names of all those who have supported this mobilisation, for justice and the law,” the statement said.

Earlier, campaign spokesman Jean-Claude Lefort said the Dignite had managed to slip past the Greek authorities because “it wasn’t spotted. It wasn’t in Piraeus, it was somewhere else.”

While the Dignite celebrated its departure, frustrated activists from the Spanish boat in the flotilla occupied the Spanish embassy in Athens on Tuesday, a diplomatic source said.

Thirty mainly Spanish activists had met with their ambassador to ask Madrid to put pressure on Greece to allow them to sail, according to one of the protesters. They then “decided to occupy the rooms,” he said.

“It’s somewhat of a symbolic occupation. There are only four activists currently in the embassy, all of whom are Spanish,” the source from the embassy said, adding that a dozen supporters were gathered in the street.

Another small boat, the Juliana, was preparing to leave the Alimos marina south of Piraeus on Tuesday, a spokesman for the boat’s Greek, Norwegian and Swedish crew said.

Meanwhile, Captain John Klusmer of the US boat Audacity of Hope was released on Tuesday without charge by a prosecutor in Piraeus, according to Jane Hirschmann, a spokeswoman for his group.

Klusmer was detained after the US boat was intercepted by coastguards Friday while attempting to break Greece’s ban. Greek authorities said they imposed a ban on the flotilla’s departure for the “safety” of the activists on board, but pro-Palestinian supporters have accused Athens of merely extending Israel’s blockade. 

An attempt by the Canadian Tahrir to set sail was thwarted Monday just minutes after it left port on the island of Crete. The Tahrir, which was carrying activists from Canada, Belgium, Italy, Switzerland and Turkey, was boarded by more than a dozen armed special forces, according to passengers on the boat, and was forced to turn back to port.

The Freedom Flotilla II had orginally intended to set sail from Greece with 12 boats and over 350 activists from 22 countries, but has come up against a stream of obstacles, including two vessels they claimed were sabotaged. Organisers have blamed Israel for sabotaging the propellers on the Irish and Swedish-owned boats and for blackmailing Greece into imposing the ban on all Gaza-bound vessels leaving its ports.

The flotilla’s planned departure coincided with the news that the president of the debt-ridden country, Karolos Papoulias, is set to visit Israel in an effort to strengthen their diplomatic and economic ties.

Activists continued to plan protests in Athens to challenge the ban, with calls for a march on Syntagma Square outside the parliament on Tuesday evening.

The Jewish state had also begun making intense preparations to foil plans by hundreds of activists to flood Israel’s Ben Gurion international airport on Friday in a show of solidarity with the Palestinians.

Prime Minister Benjamin Netanyahu ordered authorities to prepare for the “planned provocation,” which will “be dealt with in accordance with Israeli law and international law and conventions,” his office said in a statement.

Israeli media reported that flights landing on Friday from Europe would be taken to a separate terminal and all passengers carefully screened. Pro-Palestinian activists have also said they plan to arrive in their hundreds at Ben Gurion airport outside Tel Aviv on Friday to protest against Israel’s blockade of the Gaza Strip.