Gunmen stormed the house of an American aid worker in Niger, killing two people and kidnapping him, officials in the landlocked West African nation said. Residents said they had heard gunfire near the house in Abalak, a small town to the east of the capital Niamey late on 14 October.

"First they came on a motorbike and killed the guards," Ahmed Dilo, Abalak's mayor told the Reuters news agency. "Then a 4x4 came and took him away and drove towards the Mali border."

The Department of State warns US citizens travelling to or residing in Mali of ongoing terrorist attacks and criminal violence in the country, which sits to the north and west of Niger.

Dilo added that two guards had been killed in the raid, one of whom was a soldier from neighbouring Nigeria. It is US Government policy that all embassy personnel are attended by an armed Nigerian security presence.

The US man has not been identified, but a security source told the Agence France Presse (AFP) news agency that he was working for a non government organisation.

The source who did not wish to be identified added: "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."

A spokesperson for the US Embassy said an investigation had been launched but that no further details could be confirmed. However, Islamist insurgencies are relatively common in Mali, where hostages are frequently taken. No U.S. citizen has been kidnapped in Niger, until now.

Though kidnappings are thought to be rarer in Niger than in Mali, several kidnappings of Europeans have taken place in the country in the last five years. Guidance issued by the Foreign and Commonwealth advises against all but essential travel to the entire country, and against all travel to areas north of Abalak. The FCO travel advice website says there is a "high threat from terrorism, including kidnapping," due to intervention in Mali and work to counter Islamic extremist group Boko Haram.

The US State Department also warns: "The terrorist organization Al-Qaida in the Islamic Maghreb (AQIM) has kidnapped Europeans in the region and continues to threaten to kidnap Westerners, including U.S. citizens, in Niger."

Boko Haram Nigeria
Islamic extremist group Boko Haram are active in Niger and Mali Emmanuel Braun/Reuters