Riot police beat back a portion of the protesters who attempted to climb over barriers with truncheons, forcing them to retreat, images broadcast on Spanish public television showed.
A boat carrying former Barcelona mayor Ada Colau was among those prevented from proceeding. Colau and her fellow activists, including Nelson Mandela’s grandson Mandla Mandela, face deportation by Israel.
Several hundred protesters also marched outside the Irish Parliament in Dublin, where support for the Palestinian cause has often been compared to Ireland’s centuries-long struggle against British colonial rule.
Miriam McNally, who said her daughter had set sail with the flotilla, was at the Dublin demonstration.
“I am worried sick for my daughter, but I am so proud of her and of what she’s doing,” McNally told AFP.
“She is standing up for humanity in the face of grave danger.”
Around a thousand people marched in Paris’ Place de la Republique, an AFP journalist saw, while in the port city of Marseille, in southern France, around a hundred pro-Palestinian protesters were arrested in the afternoon after attempting to block access to offices of weapons-maker Eurolinks, accused of selling military components to Israel.
Protests were also held in Berlin, The Hague, Tunis, Brasilia, and Buenos Aires, according to AFP correspondents.
“Intolerable”
In Italy, where the country’s main unions have called a general strike for tomorrow in solidarity with the flotilla, thousands took to the streets to urge Prime Minister Giorgia Meloni to defend the activists.
Besides Rome, where police said 10,000 people joined a march, other protests took place in cities including Milan, Torino, Florence, and Bologna.
A day after a similar demonstration yesterday, protesters in the capital gathered at the Colosseum and marched, slamming the far-right Prime Minister’s support of Israel.
“We are prepared to block everything. The genocidal machine must stop immediately,” demonstrators chanted.
In Turkey, where the Government is among the fiercest critics of Israel’s offensive, a long column of demonstrators marched to the Israeli Embassy in Istanbul, with banners including, “Total embargo on the occupation”.
“We demand the release of all members of the Sumud fleet and all prisoners, and as university students, we demand that all academic and economic ties with the genocidal Israeli state be terminated at our universities,” 21-year-old student Elif Bozkurt told AFPTV.
Around 3000 demonstrators also took to the front of the European Parliament building in Brussels, with one banner urging the EU to “break the siege” as smoke bombs and crackers were set off in the crowd.
“The message is that each boat must be protected,” a protester named Isis told AFPTV at the demonstration, urging the European Union’s leadership to halt the “astronomical sums of money sent to Israel” through the bloc’s agreements with the Middle Eastern country.
‘Apartheid state’
A similar-sized crowd rallied in Geneva, according to an AFP journalist at the scene and Swiss broadcasters, with the mostly young protesters lighting a bonfire near the central station.
The protesters then headed to the Swiss city’s Mont Blanc bridge, at the end of Lake Geneva, to be met by a line of police in riot gear, who pushed the demonstrators back after brief clashes.
In the Greek capital Athens, a throng of protesters set off fireworks and flares.
“The attack against the flotilla Sumud, it was a barbaric escalation from the Israeli apartheid state. They don’t want to even open a passage for humanitarian help to Gaza,” Petros Konstantinou, co-ordinator of Greece’s World Against Racism and Fascism group, told AFPTV.
Dozens also rallied in Malaysia’s capital, Kuala Lumpur, in front of the embassy of the United States, Israel’s key ally.
“We are very upset ... Upset, angry, disgusted because what they are doing is for humanity,” said Ili Farhan, 43.
“They are just bringing in aid and baby food ... This arrest is unjust.”
-Agence France-Presse
