By Abdoulaye Massalaki
NIAMEY (Reuters) - Niger opposition leader Hama Amadou was arrested when he flew in to the capital on Saturday as security forces blocked off the airport, a year after he fled the country when sought by investigators probing a child trafficking ring.
Hama, a former speaker of the national assembly and ally of President Mahamadou Issoufou, had pledged in September to return to Niger to stand in a presidential election next February.
Last year he left the country before investigators could question him in an investigation in which 30 people including his wife have been charged with obtaining newborn babies from neighboring Nigeria to sell them to wealthy couples in Niger.
The government had said it would arrest Hama if he returned to the country.
"The gendarmerie proceeded on Saturday to arrest Hama Amadou in an execution of an arrest warrant against him," a security source said.
More than a dozen supporters were arrested in the morning after calling on others to welcome Hama at the airport and accompany him to party headquarters and then to his family's residence, the police said.
"There have been at least a dozen supporters of Hama who were arrested, including members of this political party bureau," said a security source.
Hama, who has said the case against him is politically motivated, will be held in prison before appearing in court.
After coming third in the first round 2011 presidential election vote, Hama threw his support behind Issoufou in the run-off, helping him win the presidency.
But when Issoufou formed a government of national unity, Hama said he had done so unilaterally and switched to join the opposition.
Several shops closed for the day and security forces blocked the airport with barricades, making travel to and from the east of Niamey near impossible.
In the afternoon, police used tear gas to disperse hundreds of Hama supporters who sought to remove a roadblock by the airport. The crowd responded by throwing stones at security forces.
Four reporters from two private Niger television stations, Labri and Niger 24, were arrested, the heads of the channels said.
Niamey Governor Hamidou Garba said on public television that a child had died when a motor cyclist hit him in an attempt to force the police barricade. Police were searching for the motor cyclist.
(Writing by Makini Brice; Editing by Hugh Lawson)