VALENCIA, Venezuela (AFP, Reuters) - Venezuela's military was hunting a group of "mercenaries" on Monday (Aug 7) who made off with weapons after an attack on an army base carried out against what they called the "murderous tyranny" of President Nicolas Maduro.

Around 20 men led by an army officer who had deserted battled troops in the base in the third city of Valencia for three hours early on Sunday, officials said.

The raid ended with two of the attackers being killed and eight captured, Mr Maduro said on state television.

The other 10 escaped with weapons taken from the facility, according to officials, who said an "intense search" was underway for them.

Mr Maduro claimed the "terrorist" group had ties to Colombia and the United States.

The incident heightened fears that Venezuela's deepening political and economic crisis could explode into greater violence, perhaps open armed conflict.

Officials insisted afterward that all was normal across the country.

Military helicopters flew overhead and tactical armored vehicles patrolled the streets in Valencia, a major northwestern city, in a climate of tension on Sunday after the attack.

Locals said a nighttime curfew was imposed. Police dispersed protesters who had set up flaming barricades across roads.

The armed forces said in a statement "a group of civilian criminals wearing military uniforms and a first lieutenant who had deserted" carried out the attack.

Mr Maduro said the lieutenant, among those captured, was "actively giving information and we have testimony from seven of the civilians."

Mr Maduro congratulated the army for its "immediate reaction" in putting down the attack, saying they earned his "admiration". Venezuela's opposition has repeatedly urged the military to abandon Mr Maduro.

But Defence Minister Vladimir Padrino, the head of the armed forces, has said the military's loyalty was unshakable.

"These attacks, planned by delirious minds in Miami, only strengthen the morale of our armed forces and the Bolivarian people," tweeted Socialist Party official Elias Jaua.

In a video posted online just before the attack, a man presenting himself as an army captain named Juan Caguaripano declared a "legitimate rebellion... to reject the murderous tyranny of Nicolas Maduro".

Speaking with 15 men in camouflage standing by him, some of them armed, he demanded a transitional government and "free elections".

"This is not a coup d'etat," he said. "This is a civic and military action to re-establish constitutional order. But more than that, it is to save the country from total destruction."

It was not known if he was the lieutenant referred to in the military statement, demoted for deserting, or whether he was another renegade officer.

That statement said the lieutenant involved had deserted three years ago and taken refuge in Miami, in the US state of Florida.

Venezuela has become increasingly isolated internationally as Mr Maduro tightens his hold on power through a contested loyalist assembly that started work this week.

The opposition, which controls the legislature, has been sidelined. Its leaders are under threat of arrest after organising protests - fiercely countered by security forces - that have left 125 people dead in the past four months.

The new Constituent Assembly, packed with Maduro allies including the president's wife and son, has quickly used its supreme powers to clamp down on dissent.

On Saturday, it ordered the dismissal of the attorney general, Ms Luisa Ortega, who had broken ranks with Maduro to become one of his most vociferous critics.

The United States accuses Mr Maduro of installing an "authoritarian dictatorship" that has turned Venezuela into an international pariah.

The United States, Brazil, Colombia, Chile, Guatemala, Mexico, Panama and Peru have slammed the "illegal" sacking of Ms Ortega.

And Argentina, Uruguay, Paraguay and Brazil have indefinitely suspended Venezuela from the South American trading bloc Mercosur for its "rupture of the democratic order".

"Each step by the Constituent Assembly is a step towards the precipice by this government," the leader of the opposition Parliament, Mr Julio Borges, told a news conference in Caracas on Sunday.

"The only thing it has left is brute force... The only thing it wants is to cling to power," he said, calling for more protests.