A Lebanese suspect with alleged links to Hizbullah and on trial in Nigeria for terrorism offenses told a court on Friday he was aware of a plot to assassinate Saudi Arabia's ambassador to Abuja.

The alleged plot, which had not previously been made public, came up during questioning of the defendant during the trial of him and two other Lebanese in high court in the Nigerian capital.

Bomb blasts that ripped through a mainly Christian area of the largest city in northern Nigeria have killed 24 people, an official said Tuesday, shattering a recent lull in insurgent attacks there.

At least four explosions were heard Monday night around outdoor bars in the Sabon Gari area of Kano, causing panic and sending clouds of smoke and dust into the air, residents said.

The death toll from a series of bomb blasts that rocked a mainly Christian area of northern Nigeria's largest city of Kano has risen to 12, the military said on Tuesday, blaming Islamist group Boko Haram for the attacks.

"Twelve persons were confirmed to have died ... while a couple of others who sustained various degrees of injuries were rushed to hospital for medical attention," a military statement said of Monday night's explosions.

The United States on Monday "strongly" condemned the recent violence in Egypt, where 72 people were killed in an attack on a rally in favor of ousted president Mohammed Morsi.

"The United States strongly condemns the bloodshed and violence" in Cairo and Alexandria, the White House said in a statement, urging the military-backed interim government to respect the rights of demonstrators.

Nigerian prosecutors on Monday widened charges against three Lebanese nationals "accused of links to Hizbullah" as their trial began with access to the courtroom restricted and the identities of witnesses concealed.

Mustapha Fawaz, 49, Abdallah Thahini, 48, and Talal Ahmad Roda, 51, have been accused of having ties to Hizbullah and plotting attacks against Western and Israeli targets in Nigeria.

Suspected members of Nigeria's Islamist group Boko Haram shot dead more than 20 civilians when a vigilante group attacked them in the northern Borno state, a military spokesman said Sunday.

"The suspected sect members came armed and fired sporadic shots that killed over twenty innocent civilians," Haruna Mohammed Sani, spokesman for the Multinational Joint Task Force (MNJTF) said.

The bodyguard of Salafist cleric Sheikh Ahmed al-Asir, who was detained two-days ago while trying to flee via Beirut Airport, has presented valuable confessions over the last month's clashes in the town of Abra.

According to As Safir newspaper published on Saturday, 30-year-old Palestinian Ali Abdul Wahad informed the Lebanese Army intelligence on his personal role in the battles in Abra near the southern city of Sidon.

A Lebanese national kidnapped by gunmen more than two weeks ago in southern Nigeria was released on Thursday, a police spokesman said.

"He was released this morning in (neighboring) Delta state. He was later brought to us in Benin City. He is in good state of health and he has been handed over to his family," Moses Eguavoen told Agence France Presse.

A girl and a policeman died in an attack in northern Nigeria Monday which the army blamed on the Islamist insurgent group Boko Haram.

The attack at the home of a Muslim cleric in Darazo, Bauchi state, was the first attributed to the extremist separatists since the start of the Muslim holy month of Ramadan.

A British national has been kidnapped by gunmen shortly after landing at the international airport in Lagos, Nigeria's largest city, a diplomat and a private security source told Agence France Presse Friday.

"There was a kidnapping of a Briton and we are working with the Nigerian authorities," said Wale Adebayo, spokesman at the Deputy High Commission in Lagos.