By Anamesere Igboeroteonwu
ONITSHA, Nigeria (Reuters) - Nigerian militants killed 46 police officers in an ambush in the north central state of Nassarawa this week, police said on Thursday.
It was not clear if the militants in Tuesday's attack were linked to Islamist sect Boko Haram, which has waged an insurgency in northern Nigeria for three years. Boko Haram and other Islamist groups usually operate further north than Nassarawa.
"Forty-six police officers were killed about 10 km (6 miles) from Lafia by members of a militia who had ambushed them on their way to an operation to arrest the leader of the militia group," police spokesman Sergie Ezegam said.
One security source said a Nassarawa based cult group without direct links to Islamists has emerged this year and becoming increasingly better armed.
Boko Haram and offshoots such as the al Qaeda-linked group Ansaru, as well as associated criminal networks, are the main threat to stability in Africa's top energy producer.
Although Boko Haram's attacks mostly occur in its northeast stronghold, its reach has grown in the last year, while Ansaru's attacks include a siege on a police barracks in the capital Abuja and violence further south.
Ansaru, dubbed a terrorist group by Britain, claimed responsibility for a January attack in Kogi state on a convoy of Nigerian soldiers en route to deployment with West African forces in Mali. Kogi is south of Abuja and borders Nassarawa.
Western governments are increasingly concerned about Nigerian militants linking up with other jihadist groups in West Africa.
Boko Haram wants to carve out an Islamic state in a country split roughly equally between Christians and Muslims. Around 200 heavily armed suspected members of the group laid siege on the northeastern town of Bama on Tuesday, leaving 55 people dead, the military there said.
Attacks by Boko Haram have killed more than 3,000 people since 2009, based on figures from Human Rights Watch.
(Writing by Joe Brock; Editing by Jon Hemming)