Nigerien opposition presidential candidate, Hama Amadou, has been arrested over child trafficking charges upon returning to the West African country from exile.

Amadou was detained on Saturday when he flew back to the Nigerien capital, Niamey, over a year after he fled the country when sought by investigators probing a child trafficking network.

“He was arrested on leaving the plane. Police presented him with a warrant issued for his arrest,” said lawmaker, Amadou Salah, adding that he “was led to a car [and taken] to an as yet unknown destination.”

Over a dozen supporters of Amadou were also detained on Saturday morning after calling on others to welcome him at the airport, police said.

In the afternoon, clashes erupted as police fired tear gas to disperse hundreds of pro-Amadou demonstrators who sought to remove a roadblock near the airport. The protesters responded by throwing stones at police forces.

Amadou, a former prime minister and national assembly president, had vowed in September to return to Niger to run in the February presidential election.

Last August, he left Niger for France before investigators could question him in a probe in which 30 people, including his wife, have been accused of obtaining newborn babies from neighboring Nigeria to sell them to wealthy couples in Niger.

Ahead of his return, Amadou had rejected the charges, calling on government officials to provide evidence in the case against him.

“If a dossier has been put together against me by my opponents, then it is time for me to present myself to the judges so that they say what the truth is,” he said.

The developments come as political tensions are running high in Niger due to extensive opposition to the election calendar drawn up by the country’s electoral commission.

Opposition groups have also criticized the constitutional court, which validates candidatures and vote results, for its “allegiance” to incumbent President Mahamadou Issoufou.

The first round of the presidential election is scheduled to be held on February 21, along with legislative polls.