A massive rally by Catalans demanding independence from Spain has put political leaders on the spot, forcing them to tackle demands for a referendum on the region's future, analysts say.

Many people in Catalonia, feeling slighted and short-changed by the central government that redistributes their taxes, want the right to vote on their political future next year.

Spanish police on Thursday arrested seven far-right activists accused of setting off an irritant gas in an attack on supporters of independence for Catalonia, leaving five people in need of medical treatment, officials said.

The group burst into a cultural center in central Madrid and set off the gas as politicians and others gathered to mark Catalonia's national day on Wednesday evening.

Catalans massed in a vast human chain stretching hundreds of kilometers along the Mediterranean coast on Wednesday, demanding independence from Spain in the face of fierce opposition from the national government.

Hundreds of thousands of people in yellow t-shirts joined in, according to organizers, yelling "Independence!".

Independence-seeking Catalans marshaled their forces on Wednesday for a 400-kilometer (250-mile) human chain in a bold push to break from Spain despite fierce opposition from Madrid.

Demonstrators in yellow t-shirts bearing the slogan "Catalan Way Towards Independence" prepared for the chain, which organizers said would unite hundreds of thousands of people.

Spanish police have detained three Britons for distributing nitrous oxide, or laughing gas, at a bar in the upmarket tourist resort of Marbella on the Costa del Sol, the interior ministry said Monday.

The manager of the bar and two female bartenders sold balloons filled with nitrous oxide, which induces euphoria and laughter when inhaled, for five euros ($6.50) a dose, it said in a statement.

Two years after vowing to end their bombings and shootings, Basque militants may soon take a further step towards disbanding ETA, western Europe's last major armed separatist group, observers say.

The Spanish and French governments refuse to have any contact with the group, blamed for 829 deaths in its four-decade campaign for an independent homeland, insisting it disarm and disband unconditionally.

Hundreds of thousands of Catalans will unite to create a 400-kilometer (250-mile) human chain on September 11, part of a spectacular campaign for independence fiercely opposed by Madrid.

Some 400,000 people aim to join hands along the entire coastline of the northeastern region of Catalonia to demand an historic redrawing of the map of Spain.

Madrid were eliminated in dramatic fashion from the race to host the 2020 Olympic Games after the first round of voting by International Olympic Committee (IOC) members in Buenos Aires on Saturday.

Both Madrid and Istanbul were tied after the first round -- meaning Tokyo topped that round -- and it had to be put to a second decisive vote to see who went out.

Young men ripped the heads off dead geese in an ancient folk festival in northern Spain on Thursday, clutching onto them as they dangled from a high wire until the birds' necks went snap.

On the annual Day of the Geese in the small Basque town of Lekeitio, about 20 participants took turns launching themselves from boats to grab hold of a goose hooked to a cable, which in turn was shaken up and down by those on shore.

The leader of Spain's debt-struck northeastern region of Catalonia all but conceded Thursday he will not hold a promised 2014 poll asserting the right to self-determination if Madrid maintains its fierce opposition.

Catalan president Artur Mas made the statement less than a week ahead of the region's September 11 national day, when separatists will attempt to form a human chain of hundreds of thousands of people across Catalonia to call for breaking away from the rest of Spain.