CARACAS (Reuters) - Venezuelan opposition legislator Gilber Caro, whose whereabouts had been unknown since an elite police unit arrested him in December, is being held in state custody and is well, his lawyer said on Tuesday.

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The Special Action Force (FAES) took Caro into custody on Dec. 20 in an operation the opposition described as illegal because he is protected by parliamentary immunity. He was indicted on charges including terrorism without the presence of legal counsel, according to his lawyer Theresly Malave.

Caro’s arrest came as President Nicolas Maduro’s government carried out a new wave of legal actions against opposition lawmakers just as opposition leader Juan Guaido’s campaign to oust Maduro was stalling.

“He is well, but he shouldn’t be there,” said Malave, who said she spent 45 minutes with him on Monday, together with one of his sisters. In a telephone interview, Malave said she could not disclose Caro’s specific location.

On Tuesday, Guaido’s Popular Will party said the FAES had detained another lawmaker, Ismael Leon, after intercepting him on a main avenue in Caracas.

Agents of the Sebin intelligence service later raided Guaido’s offices in Caracas. Pictures by a Reuters photographer showed two armed agents wearing ski masks standing at the entrance to the building.

A video shared by Guaido’s press team showed agents inside the building, at the entrance to the office.

“Cowardly dictatorship!” tweeted Guaido, who is in Europe seeking support for his campaign to remove Maduro from power. “As we are traveling... they kidnap @leon_ismael and raid our office.”

Venezuela’s Information Ministry and the state prosecutor’s office did not respond to requests for comment on Leon and Caro, who is a leading member of Popular Will. The vice-presidency, which oversees Sebin, did not answer calls seeking comment.

The opposition and United Nations have accused the FAES of carrying out extrajudicial killings across Venezuela on behalf of Maduro's administration. A Reuters investigation in November found that dozens of witness accounts contradicted the unit's claims of killing victims in self-defense. here

Maduro has denounced an “international campaign” to tarnish the reputation of the FAES and pledged to strengthen the force.

Before Caro’s arrest in December, the FAES had not carried out any high-profile political arrests and its operations had been focused in poor neighborhoods.

Caro had already spent a year and half in prison after being jailed without trial in January 2017 during anti-government protests on charges of treason and stealing military material. His lawyer at the time said Caro was innocent and authorities had planted weapons on him.