Nigeria's President Goodluck Jonathan visited the site of a deadly bombing in the capital Abuja on Friday after cutting short an African Union engagement to meet victims of the attack blamed on Boko Haram. 

Jonathan visited the Emab Plaza in central Abuja where a bomb blast killed at least 21 people on Wednesday and later went to a hospital where victims were being treated, describing the worsening Islamist insurgency as "one of the darkest phases in the history" of Nigeria. 

A bombing blamed on Boko Haram in the heart of Nigeria's capital raised fears Thursday of a worsening Islamist insurgency, with the security forces struggling to prevent attacks in remote villages and near the seat of government.

Wednesday's blast, which killed at least 21 people, shook the crowded Emab Plaza in downtown Abuja during the afternoon rush as shoppers were buying groceries an hour ahead of the country's World Cup match against Argentina.

Nigerian authorities have arrested one suspect, and killed another, after a bomb claimed 21 lives in a shopping center in the capital Abuja, a city gripped by fear of attacks by Boko Haram Islamists.

Wednesday's blast shook the Emab Plaza at 4:00 pm (1500 GMT), the National Emergency Management Agency (NEMA) said, as shoppers were buying groceries ahead of the country's World Cup match against Argentina, which kicked-off an hour later.

Nigeria's government on Wednesday denied claims that Boko Haram militants abducted 60 women and children from the country's restive northeast, saying there was no evidence despite eyewitness testimony.

Government spokesman Mike Omeri told a news conference in Abuja that there was "nothing on the ground to prove any act of abduction, as reported."

A double from Lionel Messi a day after his 27th birthday inspired Argentina to a 3-2 win over African champions Nigeria and assured them of finishing top of Group F at the World Cup finals on Wednesday.

Nigeria's defeat -- their fourth in four meetings at the finals against Argentina -- came with the considerable consolation that they still progressed to the second round as Iran lost 3-1 to Bosnia-Hercegovina in the other group game.

A loud explosion hit a crowded shopping center on Wednesday in Nigeria's capital Abuja, which has been repeatedly attacked by Boko Haram Islamists, the national rescue agency said.

"We received the information at about 4:00 pm (1500 GMT) about a blast" at the Emab Plaza, not far from the seat of government, said Manzo Ezekiel, spokesman for the National Emergency Management Agency (NEMA).

Unidentified gunmen killed 38 people, mostly women and children, in raids on two villages in northern Nigeria's Kaduna state, an area plagued by years of sectarian conflict, officials said Tuesday. 

The late Monday attacks targeted the remote villages of Fadan Karshi and Nandu in southern Kaduna, the head of the area's local government, Emmanuel Adamu Danzaria, told Agence France Presse.

Suspected Boko Haram militants have abducted more than 60 women and young girls in restive northeast Nigeria, a local official and a vigilante leader said on Tuesday.

The group was kidnapped in the last week during a Boko Haram attack on Kummabza village in the Damboa district of Borno state, which left at least 30 dead, according to residents who escaped the violence.

A bomb blast at a public health college in Nigeria's second city of Kano killed at least eight people on Monday, in the latest violence to hit an area repeatedly attacked by Boko Haram.

Body parts, burnt-out vehicles and pools of blood were visible at the bomb site on the grounds of the School of Hygiene, which lies near the heart of the ancient northern city, an Agence France Presse reporter said.

A suicide bomber on Sunday rammed his car into a military checkpoint in northeast Nigeria's Borno state near the border with Cameroon killing three soldiers in an attack blamed on Boko Haram Islamists, residents said.

Three other soldiers were also injured in the early morning attack in Gwoza town, a resident, Dahiru Yunusa, told Agence France Presse.