Kosovo Serb politician Rada Trajkovic, who is a fierce critic of the Belgrade-backed Srpska Lista party and was recently appointed adviser to Kosovo Communities and Returns Minister Nenad Rasic, spent the night in Serbian police detention at the border with Kosovo.

Trajkovic was detained on Thursday trying to enter Serbia from Kosovo, a former Serbian province that declared independence in 2008 but is not recognised by Belgrade as sovereign.

Kosovo Prime Minister Albin Kurti decried the detention as a “gross violation of human rights” while Rasic urged the so-called Quint countries – the United States, Britain, France, Germany and Italy – to help find a “civilised” solution.

Trajkovic told media on Friday she was detained by the police for four hours, after which “a young man came who introduced himself as from the Security Information Agency,” Serbia’s chief intelligence agency known as BIA.

The man took her son’s documents, “and as of now they have not returned the documents,” she said, adding that the BIA officer gave her no reason for her detention. “Up until now no has spoken to me,” Trajkovic said.

Trajkovic is an ally of Rasic, who took the post of Communities and Returns Minister in the Kosovo government after Srpska lista quit the cabinet and parliament in November and Serbs in four Serb-majority municipalities in northern Kosovo resigned public posts en masse in a dispute over Serbian-issued licence plates.

Serbian President Aleksandar Vucic branded Trajkovic and Rasic “Serbian scum from the bottom of the barrel”.

“The election of Rasic, a man who won less than one per cent, as well as Rade Trajkovic, who was on his list, shows that they want the persecution, expulsion and disappearance of Serbs in Kosovo and Metohija,” Vucic said at the time.

Kurti condemned Trajkovic’s detention as “typical retaliation against law-abiding Kosovo Serbs.”

Rasic told reporters: “It is a shameful case. Trajkovic is sick and going through a difficult period.”