Algerian security forces arrested seven Islamist gunmen on Tuesday in the remote southern area of In Amenas, close to the gas plant where a deadly attack took place in January 2013, the country's defence ministry said.

The statement did not link the militants with any group, but al Qaeda in the Islamic Maghreb and small pockets of Islamic State-affiliated fighters operate in some parts of Algeria, an OPEC producer of oil and gas.

Weapons and three vehicles were seized during the ambush of the gunmen, it said. It gave no details about what the militants were doing or plannning in the area, a desert region close to the border with Libya.

Veteran Algerian militant Mokhtar Belmokhtar was blamed for orchestrating the attack on the Tiguentourine gas plant in 2013, in which 40 oil contractors, mainly foreigners, were killed during the assault and siege that followed.

Algeria has become a key Western ally in the fight against militant Islamists in the region since emerging from its own civil war with armed Islamists in the 1990s that killed around 200,000 people.