CARACAS (Reuters) - Miguel Angel Martin says he knew he had to leave Venezuela when intelligence agents in black vehicles started tailing him, days after the opposition-run Congress named him a magistrate to an alternative Supreme Court in defiance of the government.

FILE PHOTO: People attend a session of Venezuela's opposition-controlled National Assembly to appoint new magistrates of the Supreme Court in Caracas, Venezuela July 21, 2017. REUTERS/Ueslei Marcelino/File Photo

He recounts how he was driven 500 km (310 miles) west from the capital of Caracas, took a seven-hour boat ride to the island of Curacao and caught a flight to Washington D.C., where he is now living in a hostel.

He is one of 33 magistrates who President Nicolas Maduro threatened with jail after Congress named them to a parallel tribunal last month to challenge the existing Supreme Court, which has heavily favored the ruling Socialist Party.

“I never imagined that they would have such an aggressive reaction, I think no one imagined it,” Martin said in a telephone interview. “The government has crossed the line between good and evil.”

Twenty-one others have sought similar refuge: besides Martin, seven have fled to the United States, six to neighboring Colombia - in some cases crossing the border on foot - and eight are living in the ambassadorial residences of Chile and Panama in Caracas.

Three have been arrested, and the whereabouts of the remainder is unknown.

Critics of the government say the exodus is a further sign of authoritarianism under Maduro that could become more pronounced under a heavily-criticized all-powerful legislature called the constituent assembly that was elected in July.

The opposition says the existing Supreme Court is illegally packed with Maduro supporters and accuse it of stripping the legislature of its constitutional powers after the ruling Socialist Party lost control of it in a 2015 election.

Maduro and the Supreme Court say the opposition magistrates’ designation was illegal and threatened to arrest them on July 21, the day they were named. The magistrates say security forces began hunting for them that very night.

The Information Ministry did not respond to a request for comment.

Magistrates who left the country spoke by telephone. Those in the ambassadorial residences declined to speak.

The opposition move was part of a series of protests, including four months of demonstrations, against Maduro over his leadership and the country’s crippling economic crisis that have posed the most serious challenge to his presidency since he took office in 2013.

TAKING OPPOSITION MESSAGE ABROAD

The first magistrate to be arrested was lawyer Angel Zerpa, who according to other magistrates is now being held in a small bathroom in the headquarters of the Sebin intelligence service.

The office of the Vice Presidency, which oversees Sebin, did not respond to an email seeking comment.

Magistrate Jesus Rojas was also arrested, but state television later broadcast a video in which he denied wanting to be part of the tribunal in the first place. His colleagues say he made the statements under duress.

“We know of no warrants out for our arrest, but officials had our pictures in airports around the country so that they could detain us if we left,” said Alejandro Rebolledo, an judge with expertise in money laundering who fled to the United States under circumstances he declined to describe.

The magistrates in exile plan to travel around the world to describe what they call the “rupture of constitutional order” in Venezuela and to encourage other countries to join the United States in imposing sanctions on ruling party officials.

“All the rulings that the Supreme Court produces without our signature are invalid,” said Martin, from his Washington hostel.

“For the transition in Venezuela, we already have a Supreme Court.”