CARACAS (Reuters) - Venezuela jailed two leading critics of President Nicolas Maduro on Tuesday in a fresh blow to the opposition after the election of a new political body with sweeping powers to strengthen the hand of the leftist government.

The United States imposed sanctions on Maduro on Monday, calling him a “dictator” for Sunday’s election of a constituent assembly that the opposition boycotted and denounced as an affront to democracy.

In a statement announcing the jailing of opposition leader Leopoldo Lopez and veteran politician Antonio Ledezma, the pro-government Supreme Court said they were planning to flee the country and had violated terms of their house arrest by making political statements and speaking to media.

But government opponents called the abrupt removal of the men from their homes by security forces in nighttime raids a sign of Maduro’s determination to silence rivals. It was a view shared by U.S. President Donald Trump, who issued a statement condemning “the actions of the Maduro dictatorship.”

“Mr. Lopez and Mr. Ledezma are political prisoners being held illegally by the regime,” it said, calling “for the immediate and unconditional release of all political prisoners.”

About 120 people have been killed in more than four months of anti-government street protests, including at least 10 during Sunday’s vote.

Maduro says the constituent assembly was designed to restore peace to Venezuela. Lopez and Ledezma had called for protests against Sunday’s vote. In addition to rewriting the constitution, the legislative superbody will have the power to dissolve the opposition-led congress, eliminating any institutional check on Maduro’s powers.

Lopez had been held more than three years in a military jail until last month, when he was unexpectedly released in what was seen as a potential breakthrough in the country’s political standoff.

Attempts to get the opposition and the government to reach a negotiated deal subsequently floundered, however, and allies said Lopez, 46, may have been jailed again because he rejected government proposals.

“They have kidnapped Leopoldo Lopez because he simply would not break under the pressures and false promises of the regime,” said Freddy Guevara, a legislator in the Popular Will party led by Lopez.

A U.S.-educated economist and former mayor in Caracas, Lopez is beloved by some in the opposition for his hard line anti-government stance and has become an international cause celebre.

The government sees him as an elitist coup-monger, and even some opposition sympathizers have criticized him for being hot-headed and authoritarian.

In a sign of heightening tensions, Chilean Foreign Minister Heraldo Munoz said Beatriz Ruiz and Jose Fernando Nunez, both recently appointed judges of an alternative Supreme Court by the opposition parliament, took refuge in Chile’s embassy in Caracas on Tuesday and may be granted political asylum.

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The U.S. Congress, meanwhile, mulled possible additional measures aimed at influencing Maduro. Senator Ben Cardin, the senior Democrat on the Foreign Relations Committee, said Monday’s sanctions against the Venezuelan leader were not enough, and that punitive economic measures targeting the country’s vital oil sector may be in order.

The United States is Venezuela’s No. 1 crude importer. Actions targeting Venezuelan oil would likely heap more damage onto an economy already suffering from a deep recession, food shortages and the world’s highest inflation rate.

“Our objective needs to be to help the people of Venezuela through this extremely dangerous humanitarian crisis ... and ultimately to get Venezuela back on a democratic path,” Cardin said.

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AN ARREST FORETOLD

Lopez himself suspected he would be detained again, and had recorded a video alongside his wife Lilian Tintori in which he urged Venezuelans to keep fighting if he was put back behind bars.

“If you’re seeing this video it’s precisely because that’s what happened, they jailed me again, illegally and unjustly,” said Lopez, in the video shown on social media on Tuesday.

Blamed by many for rising poverty in Venezuela, Maduro has faced almost daily protests demanding freedom for jailed politicians, early elections to replace him and permitted entry of humanitarian aid such as food and medicines.

Lopez and Ledezma were both taken from their homes to Ramo Verde, a military jail in a slum area about an hour’s drive from the capital, according to lawyers and family.

Lopez was originally arrested for his role in leading street demonstrations against Maduro. Ledezma, a 62-year-old veteran politician, had been arrested on charges of plotting a coup.

Condemnation of Tuesday’s arrests also came from the United Nations human rights chief, the president of the European Parliament and other governments.

“We express our solidarity with Leopoldo Lopez, Antonio Ledezma and other political prisoners in Venezuela,” Mexico’s Foreign Minister Luis Videgaray said on Twitter.