BELGRADE (Reuters) - Montenegrin police arrested Nebojsa Medojevic, a lawmaker and a prominent opposition leader, on Friday after a high court ordered he serve a two-month jail sentence passed in March for refusing to testify about high-level corruption.

Medojevic, an outspoken critic of long-serving President Milo Djukanovic and his Democratic Party of Socialists, was seized as he left parliament, a political ally said.

“This is a ... scandal, to arrest a lawmaker for something he has said,” Andrija Mandic, whose Democratic Front alliance is close to Medojevic, told reporters.

“Someone is out to stir up conflict in Montenegro,” he said.

He said Medojevic was arrested without being first stripped of his parliamentary immunity from prosecution.

Medojevic is head of the largely pro-Western Movement for Changes party which is a part of the Democratic Front, a broad alliance which is against the decades-long rule of Djukanovic and his party whom they accuse of corruption and cronyism.

Most of the other DF member parties, ranging from hardline Serb nationalists to Communists, are also against Montenegro’s membership in NATO and want closer ties with Russia and Serbia.

In March, a court fined Medojevic 1,000 euros for refusing to testify about a claim that former Podgorica mayor Miomir Mugosa bribed Special Prosecutor Milivoje Katnic with 100,000 euros in an abuse of office and corruption case. Both Katnic and Mugosa denied the charge.

Medojevic refused to pay the fine and the court sentenced him to two months in jail. He appealed, but in a statement on Friday the Higher Court said the appeal had been rejected.

Medojevic is “to remain in prison ... until testifying or until ... questioning becomes unnecessary or until the end of court proceedings, but no more than two months,” the court said.

Montenegro, the newest NATO member, wants to join the European Union, though it must first reform the rule of law and eradicate corruption, nepotism and red tape.

Last year, it opened a trial of 14 people, including Mandic, accused them of a 2016 plot with Russian agents to kill Djukanovic, the then prime minister and bring the DF to power. Moscow has rejected the accusations.