Venezuela's security forces arrested at least 14 army officers on suspicion of "rebellion" and "treason" in the first week of protests against President Nicolas Maduro's government in early April, according to military documents.
The soldiers, who include colonels and captains, are being held in Ramo Verde prison in the hills outside Caracas, according to lists being circulated within the military.
The documents said their cases were being "processed", and it was not clear if they had been formally charged.
The lists emerged after allegations by Venezuelan opposition leaders that a purge is underway within the military to quash dissent over the handling of massive demonstrations against the socialist government.
Protesters have been demanding general elections, foreign humanitarian aid and freedom for jailed activists since early April.
The documents only went up to April 8, after which opposition leaders and rights activists say many more soldiers have been rounded up.
The military's National Guard unit has been at the forefront of policing the protests, using tear gas, water cannons, and rubber bullets against masked youths who hurl stones, Molotov cocktails and excrement against security lines.
At least 65 people have died, with victims including government and opposition supporters, bystanders and members of the security forces. Hundreds more have been injured.
Opposition leaders say there is increasing disquiet within the military over the use of force against protesters.
In public, top military officers have backed Maduro's accusation that an "armed insurrection" is being mounted by violent conspirators seeking a coup with US backing.
But privately some National Guard members have complained of exhaustion and disillusionment.
A few soldiers have gone public with their discontent.
Three lieutenants fled to Colombia and requested asylum last month. The Venezuelan government demanded their extradition to face charges of coup plotting.
Opposition media last week published a video purporting to be a Venezuelan naval sergeant expressing his dissent and urging colleagues to disobey "abusive" and "corrupt" superiors.
"I reject Mr. Nicolas Maduro Moros as an illegitimate president and refuse to recognize his regime and dictatorial government," Giomar Flores said in a seven-minute video.
It showed him wearing a white naval uniform and black beret next to a Venezuelan flag.
Neither the Information Ministry nor the Armed Forces responded to requests for information.
Late leader Hugo Chavez turned the military into a bastion of "Chavismo" after a short-lived coup against him in 2002.
Though Maduro, 54, does not hail from the army as Chavez did, he has kept ties strong, placing current or former soldiers in a third of ministerial posts, and giving them control over key sectors like food distribution.
US calls for free elections
The US denounced the government of Venezuelan President Nicolas Maduro on Tuesday for suppressing protests and called for free elections.
"This is an economic, political and humanitarian crisis that demands the world's attention," Nikki Haley, US ambassador to the UN, told a US-hosted panel of Venezuelan activists and experts held in Geneva.
"The Venezuelan government is in the midst of destroying human rights and democracy in Venezuela," she said.