Gunmen have kidnapped a Lebanese national from a construction site in southern Nigeria, where abductions for ransom occur frequently, authorities said on Tuesday.

The assailants kidnapped Sani Youssef, an employee with Lebanese-owned Setraco Nigeria Limited construction company in Benin City in the southern state of Edo on Monday, police spokesman Moses Eguavoen told Agence France Presse.

Gunmen believed to be Boko Haram Islamists attacked a secondary school in Nigeria's restive northeast on Saturday, killing 42 people, many of whom were students, a medical worker and residents said Saturday.

But a military spokesman said 20 students and one teacher were killed in the dawn attack at Yobe state.

Gunmen suspected to be ethnic Fulani herdsmen invaded a farming village in restive central Nigeria's Benue State, burning several houses, police said Saturday, amid reports that at least 20 people died in the violence.

"There was an attack yesterday, around 11:00 am by suspected Fulani cattle rearers at Iyordye Akaahena village in Guma ... Many houses were burnt," state police spokesman Daniel Ezeala told Agence France Presse.

A military commander claimed on Wednesday that soldiers had since last week killed more than 100 attackers responsible for a deadly raid in ethnically divided central Nigeria.

"So far we have killed more than 100 of the attackers before we succeeded in securing the areas," Major General Henry Ayoola, who commands a task force in the region, told reporters.

Raids by gunmen in ethnically divided central Nigeria and gun battles between soldiers and attackers have killed at least 48 people and left dozens of homes burnt, the military said Friday.

The attacks appeared to have been reprisals linked to cattle theft, often the source of friction in the Middle Belt region dividing the mainly Muslim north and predominately Christian south of Africa's most populous nation.

Nigeria on Wednesday charged three Lebanese allegedly linked to Hizbullah with "terrorism related offenses."

Five Lebanese were implicated last month after a huge cache of arms and ammunition was found in their premises in the northern city of Kano and the capital Abuja.

Britain is planning to force visitors from India, Pakistan, Nigeria and other countries whose nationals are deemed to pose a "high risk" of immigration abuse to provide a cash bond before they can enter the country, a report said Sunday.

The Sunday Times newspaper said that from November, a pilot scheme would target visitors from those three countries plus Bangladesh, Sri Lanka and Ghana.

An armed gang has raided a northern Nigerian village and killed 48 people in an apparent reprisal attack targeting a local vigilante group, a state official said Wednesday.

"There was an attack by armed bandits early Tuesday on Kizara village where 48 residents were killed in apparent targeted killings by cattle rustlers that have been terrorizing the state for some time now," said Ibrahim Birnin-Magaji, commissioner for information in Zamfara state, where the village is located.

Suspected Islamists shot dead nine students as they sat an exam in an attack on a private school in Maiduguri, northeast Nigeria, local people said Tuesday.

The attack, in a region that is a stronghold of the Islamist rebel group Boko Haram, happened on Monday in the Jajeri suburb of the city, they said.

At least 9,000 people have fled violence in northern Nigeria and crossed into neighboring countries as a government offensive aims to end a four-year Islamist insurgency, the U.N. said on Tuesday.

In addition to those refugees, a local official in northeastern Nigeria, where the violence has been concentrated, has said some 19,000 wheat and rice farmers have been chased away from fields, raising concerns over potential food shortages.