CARACAS, Venezuela (AP) — Venezuela’s top prosecutor on Wednesday ordered the arrest of a dozen opposition members, including former National Assembly leader Juan Guaidó and three campaign staffers of presidential candidate Maria Corina Machado.

Attorney General Tarek William Saab accused them of conspiring against the referendum the government held Sunday to claim sovereignty over a large swath of neighboring Guyana that Venezuela has long argued was stolen when the border was drawn more than a century ago.

Saab did not present any evidence during the nationally televised announcement of treason, conspiracy and other charges against the 12 government adversaries, only three of whom now live in Venezuela. He also linked to the case Savoi Jadon Wright, a U.S. citizen arrested Oct. 24 during a visit to Venezuela.

Saab alleged the opposition members worked together to affect the outcome of the referendum. He accused Wright of using cryptocurrencies and cash to “avoid financial controls and mask the origin and destination of the funds used” in the purported conspiracy.

The announcement came as the government continued to defend the turnout figure it reported after Sunday’s vote. The government said about 10.5 million people — just over half of eligible voters — cast ballots, but that figure defied what people witnessed at voting centers, where long lines typical of Venezuelan elections never formed.

President Nicolas Maduro’s government held the referendum to supposedly allow Venezuelans to decide the future of the oil- and mineral-rich Essequibo region of Guyana.

Maduro’s government promoted the five-question referendum for weeks as a unifying act of patriotism, including theater performances and reggaeton music. Venezuelan voters were asked whether to support establishing a state in Essequibo, grant citizenship to its residents and reject the jurisdiction of the United Nations’ top court in the dispute.

Of the 12 people facing arrest, only Machado’s three campaign workers are in Venezuela. They were at a news conference called by Machado when Saab announced the charges against them.

Machado was the winner of an Oct. 22 presidential primary organized by a faction of Venezuela’s opposition without the government’s assistance. That election surpassed participation expectations, including in neighborhoods considered strongholds of the governing socialist party.

Primary organizers said more than 2.4 million voters participated, a number that government officials declared mathematically impossible given the number of available voting centers and the time it would take a person to cast a paper ballot in the opposition election. After the election, Saab opened investigations against its organizers.

Machado told reporters the lackluster turnout in the Essequibo referendum was “a monumental defeat” for Maduro’s government and called the actions against her campaign staffers “a big mistake.”

“They are making a mistake, and they are not going to stop us,” she said. “On the contrary, this gives us more strength.”

Wright’s family has said he was wrongfully arrested and being held for tens of thousands of dollars in ransom. He was detained just days after the U.S. government eased crippling oil sanctions on Maduro’s administration.