Reports of Boko Haram militants joining Islamic State (Isis) fighters in Libya are a cause for concern, according to a senior US official. A summit on the battle against Boko Haram is taking place in Nigeria on Saturday, 14 May. At the conference will be the world's heads of state, including UK Foreign Secretary Philip Hammond, US Deputy Secretary of State Antony Blinken, French President François Hollande and representatives from Niger, Chad, Cameroon and Benin.

The 15-member UN Security Council expressed "alarm at Boko Haram's linkages with the Islamic State", according to a statement. Support for Nigerian President Muhammadu Buhari's "crucial initiative" to hold the security summit in Abuja was also welcomed.

Blinken said he was alerted to reports that Boko Haram fighters were heading to Libya, where Isis (Daesh) influence and support has grown recently.

"We've seen that Boko Haram's ability to communicate has become more effective," he said in a BBC report. "They seem to have benefited from assistance from Daesh [IS]," he added.

Blinken added: "So these are all elements that suggests that there are more contacts and more co-operation, and this is again something that we are looking at very carefully because we want to cut it off."

He also refused to comment on whether the US would grant a Nigerian request to sell them American war planes in their battle against Boko Haram. However, in a Guardian report, US officials said Washington wants to sell up to 12 A-29 Super Tucano light attack aircraft to Nigeria. The deal is awaiting approval from Congress.

On 7 March 2015, Abubakar Shekau, leader of the Nigerian terrorist group, announced his allegiance to Abu Bakr al-Baghdadi, the self-proclaimed leader of IS. In Boko Haram's seven-year effort to create an Islamic state in Nigeria, over 20,000 people have been killed, while millions have fled.