A Vietnamese pop star and pro-democracy advocate has been detained as part of an increasingly bold crackdown on dissidents in the one-party communist state.

Mai Khoi, a singer-songwriter, was returning home from performing in Europe when she was detained at Hanoi airport and taken for questioning, Human Rights Watch said.

She has long been on the radar of Vietnam’s authorities, taking heat for her pro-democracy views. In the past she has been harassed, evicted and had her concerts shut down, but until now she has been able to travel freely.

“Mai Khoi is someone who they [Vietnamese authorities] are certainly interested in and they see her as a dissident, but she is someone who is high-profile enough that they would basically leave her alone,” said Phil Robertson, HRW’s deputy Asia director.

“This is the first [time] we have seen her subjected to the kind of things that your ordinary dissidents would face when they are trying to come back from overseas.”

Singing about reform & demanding rights should not be a crime, so #Vietnam must release singer Mai Khoi from detention at airport. @hrw demands her immediate release & an end to systematic harassment of activists peacefully expressing their views. @MOFAVietNam pic.twitter.com/uigCVEmKsC — Phil Robertson (@Reaproy) March 27, 2018

Mai Khoi has not shied away from controversy in Vietnam, a country with heavy state media censorship and where bloggers and activists are beaten, threatened and intimidated.

During a visit by Donald Trump to Vietnam last November, Mai Khoi held up a banner along the planned route of his motorcade bearing the words: “Piss on you Trump”.

“I was just protesting the way any American would protest, I haven’t done anything wrong,” she reportedly said at the time.

After that demonstration, Mai Khoi and her Australian husband, Banjamin Swanton, were told they were being evicted from their apartment in the Vietnamese capital.

In 2016 Mai Khoi nominated herself to run for the national assembly on a pro-democracy platform. A year earlier she met Barack Obama, then US president, when he visited Vietnam.

According to information on her website, since running for parliament Mai Khoi has effectively been banned from performing in Vietnam.

It is unclear what prompted authorities in Vietnam to detain her now. Robertson said the government had intensified its crackdown on rights activists in recent months.

“The authorities are getting bolder,” he said. “I think the Vietnam government feels that the US and other countries are busy somewhere else and this gives them ample running room to crack down on the dissidents the way they have wanted to in the past.”