Holding candles, people march on one of the city's main avenues to protest against the National Court's decision to imprison civil society leaders without bail, in Barcelona, Spain, Tuesday, Oct. 17, 2017. Spain's top court also ruled Tuesday that a recent independence referendum in Catalonia was unconstitutional, a day after a Madrid judge provisionally jailed two Catalan independence leaders, Jordi Sanchez and Jordi Cuixart, in a sedition probe.(AP Photo/Manu Fernandez)

BARCELONA, Spain - The Latest on Catalonia's drive for independence (all times local):

8:40 p.m.

Thousands of people are protesting in Barcelona to demand the release of two Catalan pro-independence activists jailed a day earlier by Spanish authorities in a sedition case.

The demonstrators have flooded a main avenue, holding up candles, pro-independence "estelada" flags and chanted "political prisoners, freedom."

The jailed activists are Jordi Sanchez and Jordi Cuixart, who lead two different grassroots groups.

On Monday, a Madrid judge provisionally jailed Sanchez and Cuixart in a sedition investigation. The judge ruled they were behind huge demonstrations Sept. 20-21 in Barcelona that hindered the police operation against preparations for an Oct. 1 independence referendum.

Spain's top court has ruled that the referendum was unconstitutional, adding legal weight to the government's efforts to block an attempt by the region to break away from Spain.

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3:20 p.m.

A Catalan official says the jailing of two prominent Catalan separatist activists shows how the central Spanish authorities in Madrid are choosing "repression over dialogue."

The Spanish government has said no dialogue can take place if Catalan independence on the table because reforming Spain's Constitution in the national parliament is the only legal way a region can secede.

Prime Minister Mariano Rajoy's conservative government has threatened to take over some or all of Catalonia's regional powers if separatist authorities don't fall in line by Thursday morning.

Catalonia cabinet spokesman Jordi Turull, however, says central authorities don't need to wait for the deadline. He says "from now to Thursday, the state has the opportunity to sit down and talk." Noting the victory of the region's dispute Oct. 1 independence vote, Turull said "surrendering is obviously not part of this government's plan."

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2:45 p.m.

Spain's top court has officially ruled that Catalonia's disputed independence referendum was illegal because a regional law that backed it was against Spain's constitution.

The Catalan regional parliament passed the so-called "self-determination referendum law" in early September. Regional leaders went on to stage the Oct. 1 referendum on whether the region should separate from Spain.

Spain's constitutional Court had earlier suspended the law temporarily while judges assessed the Spanish government's objection to it.

In its ruling Tuesday, the court says the law was against national sovereignty and the "indissoluble unity of the Spanish nation."

The court says that the parliamentary session that approved the law was also illegal.

Catalan government spokesman Jordi Turull says he is not surprised. "We are facing an executive power in the state that uses the judiciary branch to block the legislative," he said.

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11:40 a.m.

Protesters are gathering for a fresh round of demonstrations in Barcelona to demand the release of two leaders of Catalonia's pro-independence movement who were jailed in a sedition probe.

A Madrid judge on Monday provisionally jailed Jordi Sanchez and Jordi Cuixart, the leaders of grassroots organizations Catalan National Assembly and Omnium Cultural.

The judge ruled they were the orchestrators of massive demonstrations Sept. 20-21 in Barcelona that hindered a police operation against preparations for the Oct. 1 independence referendum.

Protests have been called at midday Tuesday in Barcelona, the Catalan capital, and an evening demonstration is also planned.

Thousands of supporters, carrying posters reading "Freedom for the political prisoners" banged pots and pans and honked car horns in Barcelona following the jailing Monday.

News from © The Associated Press, 2017