Ebola-hit nations met for crisis talks on Thursday as the death toll topped 1,500 and the World Health Organization warned that the number of cases could exceed 20,000 before the outbreak is stemmed.

Nigeria announced that the virus had reached its oil-producing hub, dashing hopes that the country had successfully contained it to its biggest city, Lagos.

The U.N. Security Council on Wednesday asked African countries of the troubled Sahel region to set up regional patrols to better protect their borders from organized crime and terror groups.

In a unanimously adopted statement, the council expressed concern for the "alarming situation" in the region, citing groups such as al-Qaida in the Islamic Maghreb (AQIM), Nigeria's Boko Haram and Mali's Ansar Dine.

Nigeria's oldest preacher, who seven years ago married a woman 77 years his junior, has died, church officials said on Wednesday. He was said to have been 114.

The Reverend Samuel Akinbode Sadela died on Sunday after a brief illness associated with old age, a senior official in his Gospel Apostolic Church in the Gbagada district of Lagos told Agence France Presse.

A Lebanese expatriate, who was kidnapped in Nigeria, was released for ransom, reported the National News Agency on Wednesday.

It said that Saadallah al-Seqlawi was abducted some ten days ago by gunmen in Nigeria.

Nigeria said Tuesday that two more people had been released from isolation after recovering from Ebola, leaving only one living patient with the disease in the country.

According to the health ministry, Nigeria has recorded 13 confirmed cases of Ebola, including the Liberian-American Patrick Sawyer, who brought the virus to the economic capital Lagos on July 20 and died five days later.

Boko Haram's declaration of a caliphate in Nigeria may have been prompted by the attention heaped on Islamic State (IS) militants in Iraq, experts said, but the pronouncement may have deeper roots.

The Nigerian group announced in a video obtained by Agence France Presse on Sunday that the captured town of Gwoza in northeastern Borno state was under an Islamic caliphate, drawing comparisons with a similar declaration by IS in June.

Boko Haram has seized control of a Nigerian town after soldiers deployed there fled to take refuge across the border in nearby Cameroon, a police source said Tuesday.

"Boko Haram fighters moved into Ashigashya" overnight Monday, where they slaughtered three people in front of a church, a Cameroon police source told Agence France Presse on condition of anonymity.

Hundreds of Nigerian soldiers fled across the border to neighboring Cameroon because of fears of attack from Boko Haram Islamists, Cameroon security sources told Agence France Presse on Monday.

A Boko Haram attack on a border town in northeast Nigeria forced thousands of people to flee on Monday, in a fresh assault indicating the militants' growing ability to strike at will.

The attack on Gamboru Ngala comes after the town was almost entirely destroyed in May in a devastating assault that also left more than 300 people killed and prompted outrage at the lack of military response.

Boko Haram's leader said a northeast town seized by the insurgents earlier this month has been placed under an Islamic caliphate, in a video obtained by Agence France-Presse on Sunday.

"Thanks be to Allah who gave victory to our brethren in (the town of) Gwoza and made it part of the Islamic caliphate," Abubakar Shekau said in the 52-minute video.