Venezuela's military said Sunday it repelled a "terrorist" attack on a base in the city of Valencia, led by an army deserter allegedly linked to "foreign governments."
Two of the attackers were killed and eight were captured, President Nicolas Maduro said on state television, claiming the group of "mercenaries" -- whose total number he put at around 20 -- had ties to Colombia and the United States.
Officials insisted afterward that all was normal across the country. 
Still, the incident heightened fears that Venezuela's deepening political and economic crisis could explode into greater violence.
In Valencia, a major northwestern city, military helicopters flew overhead as tactical armored vehicles patrolled the streets in a climate of tension. 
Locals said a nighttime curfew had been imposed, as flaming barricades set up in the street by anti-government protesters spewed black smoke.
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, during which a number of weapons were stolen.
The lieutenant and several of the attackers were arrested but "an intense search" was on for the others who made off with the arms, the military said.
Maduro said the captured lieutenant was "actively giving information and we have testimony from seven of the civilians." 
- Maduro 'dictatorship' -
Maduro congratulated the army for its "immediate reaction" in putting down the attack, saying they earned his "admiration."
Venezuela has become increasingly isolated internationally as Maduro has tightened 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 organizing protests, fiercely countered by security forces, that have left 125 people dead in the past four months.
One prominent leader, Leopoldo Lopez, was returned to house arrest after being hauled off to military prison four days ago. 
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, Luisa Ortega, who had broken ranks with Maduro to become one of his most vociferous critics.
On Sunday it announced -- then suspended -- the creation of a "truth commission" sought by Maduro to probe alleged crimes by the opposition.
The United States accuses Maduro of installing an "authoritarian dictatorship" that has turned Venezuela into an international pariah.  
The United States, Colombia, Chile, Guatemala, Mexico, Panama and Peru have slammed the "illegal" sacking of 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."
- Loyal military chiefs -
"Each step by the Constituent Assembly is a step towards the precipice by this government," the leader of the opposition parliament, 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.
The opposition has repeatedly urged the military to abandon Maduro. 
But Defense Minister Vladimir Padrino, the head of the armed forces, has said the military's loyalty was unshakable.
After Sunday's attack in Valencia, Padrino tweeted that the assailants "couldn't do anything against" the army. 
"They try to assault it with terrorist attacks. They can't," he said.
In a video posted online just before the attack, a man presenting himself as an army captain declared a "legitimate rebellion... to reject the murderous tyranny of Nicolas Maduro." 
Speaking with 15 other men dressed in camouflage standing by him, some of them armed, he demanded a transitional government and "free elections."
It was not known if he was the lieutenant referred to in the military statement.
That statement said the officer had deserted three years ago and taken refuge in Miami, in the US state of Florida. 
The deputy leader of Maduro's Socialist Party, Diosdado Cabello, tweeted that there was "absolute normality in the other military units in the country."