NIAMEY (AFP) - An American non-governmental organisation (NGO) worker was kidnapped on Friday (Oct 14) night in the Niger town of Abalak, north-east of the capital Niamey, before being taken by his abductors to Mali, a security source told AFP.

"An American NGO worker was kidnapped Friday around 9pm local time in Abalak. It is too early to determine the identity of the kidnappers who have returned to Mali. The authorities have put the region on maximum alert," the source said, asking not to be named.

"At least two people were killed during an exchange of gunfire" as the hostages were being taken, the source said, without revealing the identity of the victims. "All roads to Mali are being monitored."

It is the first time that a US national has been kidnapped in Niger.

A US State Department spokesman told AFP said they were aware of reports of the kidnapping of an American citizen, but declined to comment further.

Niger's long, porous borders make it occasionally vulnerable to the armed violence that has rocked neighbouring states including Mali in recent years.

Northern Mali, which fell under the control of Al-Qaeda-linked groups in 2012 before a French-led military intervention pushed them out, remains subject to attacks by militants.

In January 2011, two young French people were kidnapped from a restaurant in Niamey and were killed shortly afterwards during a rescue attempt.

The previous year, five employees of the French energy firm Areva were kidnapped by Al-Qaeda in the Islamic Magreb (AQIM) from a uranium mine in Arlit, north of the country. Four men were freed in 2013 after the earlier release of the sole female hostage.

Earlier this month, 22 soldiers from Niger were killed during an attack by armed men who came from Mali to target a refugee camp in the Tahoua region, northeast of Niamey.

Three soldiers were also injured, according to Niger's army, which has been deployed along the country's longer border with Mali to prevent armed groups getting in. Niamey is also calling for a diplomatic solution to the conflict in Mali.

"To resolve the security problem in Mali is also to resolve the security problem in Niger", Niger's president Mahamadou Issoufou said during a meeting with German Chancellor Angela Merkel this week.

Niger also faces constant attacks in the south-east of the country from Nigerian militant group Boko Haram.