Niamey - Niger has rounded up close to 150 migrants crossing the Sahara to Algeria in the past two days, in a crackdown on illegal migration after 92 people died of thirst trying to make the same desert journey.
The grisly discovery on Wednesday of the bodies of mostly women and children left stranded in the harsh Sahara desert after their trucks broke down, has prompted Niamey to clamp down on migrant trafficking networks.
A security source said on Saturday that around 100 migrants, mostly men and some children, had been stopped in the desert and placed in police cells in the northern town of Arlit, a transit point for people seeking passage to Algeria.
"The migrants are being held at the gendarmerie but we do not yet know what will become of them," said the security source.
According to an aid group in Arlit, the group was travelling on board two lorries and three pick-up trucks.
Niger's government earlier announced it had "intercepted" 47 other migrants on Friday headed for Assamaka, the last town in Niger on the route to Tamanrasset, in southern Algeria.
Tamanrasset was the intended destination for the 92 migrants whose bodies were found decomposed in the desert.
Gut-wrenching details have emerged about the deaths of the 52 children, 33 women and seven men in early October.
Stranded, thirsty and desperate, some of them set out for help. Nineteen reached Tamanrasset alive, while another man walked to Arlit and a woman was saved by a driver who came across her in the desert.
The bodies, some of them eaten by jackals, were found in different locations across a 20km radius.
A resident of Tamanrasset who organised the deadly voyage has been imprisoned in Arlit, a security source said.
Niger's Prime Minister Brigi Rafini made an appeal to his countrymen on Saturday not to attempt illegal migration but rather to stay at home.
"We must all pull together.... People must understand that their happiness is to be found in Niger and that they must do everything to stay," said Rafini on a visit to the southern city of Kantche, where 70 of the 92 victims came from.
A judicial investigation has been opened into the tragedy, the governor of the main northern town of Agadez Colonel Garba Maikido said on national radio.
"We cannot remain indifferent in the face of this tragedy. We must take measures so that this type of tragedy never happens again on our territory."
Niger on Friday ordered the immediate closure of migrant camps in Agadez and vowed those involved in human trafficking would be "severely punished".
"This tragedy is the result of criminal activities led by all types of trafficking networks," the government said as it announced the closure of the "ghettos", the name given to the migrant camps.
On Saturday, Agadez prosecutor Samna Chaibou laid out further measures to control the flow of migrants.
He said any migrant without travel documents would be "turned back", specifying that they should have valid papers with a visa for the country they want to visit.
Niamey is also targeting people-smugglers, and the drivers of vehicles transporting people across the desert will have to declare the identity of the migrants or face criminal charges.
The landlocked country, from where migrants try to reach Algeria or Libya, is almost three times the size of California, and 80 percent of its landmass is covered by the Sahara desert.
Migrants are often found dead in the north African desert, frequently abandoned by people-smugglers to their fate, but not usually on the scale of the latest tragedy.