CARACAS (Reuters) - Opposition lawmaker and oncologist Jose Manuel Olivares, who led protests over Venezuela’s crumbling health sector, has fled for neighboring Colombia after being told that his relatives could be arrested unless he quit politics.

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Olivares said the SEBIN intelligence service grew increasingly aggressive after his brother was arrested last year and detained for several months in what Olivares called an arbitrary detention meant to intimidate him.

At the end of last week, Olivares received a phone call from a man who identified himself as a member of the SEBIN.

“He said I had not learned my lesson with my brother, and informed me that they had arrest warrants against my wife, my mother, and my brother,” Olivares told Reuters on Friday, adding that SEBIN patrols were also regularly visiting his relatives’ homes.

After that phone call, the 32-year-old lawmaker who represented the coastal state of Vargas decided to flee.

Over the weekend, Olivares and his wife, brother, and three-month-old son drove 18 hours to the Colombian border, which they crossed illegally because the baby had not been granted a passport.

Colombia’s center-right government, a fierce critic of leftist Venezuelan President Nicolas Maduro, has allowed them in despite the child’s lack of papers and the family is now in the capital Bogota, Olivares said.

“We left the country in a traumatic way. I am going to have to work now, hopefully as a doctor but I might have to do anything, like so many other Venezuelans around the world,” Olivares said in allusion to impoverished Venezuelan immigrants who increasingly wait tables, construct buildings and sell street food across Latin America.

Olivares’ departure further swells the ranks of opposition activists forced into exile, arrested, or barred from politics during Maduro’s crackdown on dissent.

The lawmaker had been at the forefront of protests decrying medicine shortages, crumbling health infrastructure, and a mass emigration of doctors. He also helped organize research into the state of hospitals after the Health Ministry stopped publishing key data on disease and infant mortality.

“Maduro’s government thinks that with this persecution they hurt me or weaken me, but it is the complete opposite,” Olivares wrote on Thursday night in a letter posted on Twitter announcing his departure. “They are the ones exposing themselves, because of their evil and cowardice as they persecute my family and newborn son, as well as because of the fear they have of people protesting and demanding their rights.”

Venezuela’s Information Ministry did not respond to a request for comment.

Maduro says the opposition is a coup-plotting elite seeking to topple him by sabotaging the economy. Most economists instead blame Venezuela’s creaking state-led system for shortages, hyperinflation, and five years of economic contraction.