Niger's army has clashed with a heavily armed convoy travelling from Libya towards Mali, security sources say.
Defence Minister Mahamadou Karidio said that one soldier was killed in the clashes on Sunday while several attackers were captured.
Mr Karidio did not clarify whether or not the convoy was made up of fighters of the ousted Libyan regime or al-Qaeda linked militants.
Both groups have travelled through the increasingly unstable border area.
The remote desert region is also affected by a rebellion involving ethnic Tuaregs, some of whom fought on the side of killed Libyan leader Col Muammar Gaddafi during the conflict in Libya.
Serge Hilpron, the head of Radio Nomad, a broadcaster in northern Niger, told the AP news agency that his sources indicated that both Libyan nationals and Tuaregs were in the convoy.
"Because of the Libyan problem, there are now traffickers heading to Libya to pick up the arms left behind and to bring them here. These same traffickers then sell the arms to AQIM [al-Qaeda in the Islamic Maghreb]," he is quoted as saying.
Mr Karidio said the military captured some of the fighters during the clashes in the Arlit area.
One soldier was killed and four wounded in the fighting, he said.
Security sources told France's RFI radio that six four-by-four vehicles, with a large quantity arms from Libya, were destroyed.
Mr Karidio said a huge arms cache was seized, including rocket-propelled grenades and assault rifles, but he did not specify where they came from.
Security experts believe AQIM - which attacks and kidnaps foreigners across the region - is acquiring weapons from Libya, which they describe as an "arms bazaar".
Reports from last month claimed a son of Col Gaddafi, Saif al-Islam, was in a convoy heading towards Libya's desert border with Niger, but the reports were never confirmed.
In September, Niger's government said another son of Col Gaddafi, Saadi, had crossed into Niger and had been given refuge in the capital, Niamey.
The US has pledged to help Libya's National Transitional Council to recover missing weapons, including surface-to-air missiles.
Last month, the National Movement for the Liberation of the Azawad rebel group - made up of Tuaregs - emerged in Mali.
It said it would absorb Tuareg fighters returning from Libya.
Col Gaddafi was a strong backer of Tuaregs in Niger and Mali, who claim they are marginalised by the governments of the two countries.