Security chief Milciades Avila is set to appear in court every 30 days, Machado said in a post on X on Thursday, in which she thanked people for their support and contribution to "reverse this injustice."

Avila was detained in the early hours of Wednesday on charges of violence against a group of women who had reportedly tried to attack Machado alongside opposition coalition candidate Edmundo Gonzalez at a food store in Aragua state over the weekend.

His arrest came less than two weeks before the July 28 vote, where Gonzalez is polling significantly ahead of President Nicolas Maduro, who is seeking a third term.

Venezuela's opposition has repeatedly denounced arrests and other moves by the authorities that they say are meant to harm its election campaign and prevent a fair election. The government denies the allegations.

Machado, who resoundingly won the opposition's October primary, was barred by a court from running in the election over alleged fraud, which she denies. Several dozens of her allies have also been detained.

Machado's lawyer Omar Mora celebrated the release on social media.

"Little by little we will dismantle the reckless and false accusations against you! We will continue working for freedom and the return of justice to Venezuela," he said on X.

The election is being closely monitored by the United States, which has tied its lifting of sanctions to Venezuela's implementation of free elections. It re-imposed sanctions in April, saying Maduro had failed to meet commitments.