Boko Haram was unable to disrupt elections in Nigeria but its allegiance to Islamic State shows the group has an agenda that reaches well beyond Africa's most populous country, a UN envoy said today.

Mohammad ibn Chambas, the UN envoy for West Africa, told the Security Council that while Boko Haram fighters staged attacks on election day in Bauchi state, northeast Nigeria, "they didn't have an impact on the voting process."

"Boko Haram was unable to disrupt the electoral process," he told the 15-member council.

Nigerians voted Saturday and yesterday in presidential and parliamentary elections, one of the closest in the country's history, amid fears of violence.

Chambas said that Boko Haram's announcement that it had pledged allegiance to the Islamic State group, "whether for publicity reasons or to tap into ISIL support," shows that "Boko Haram's agenda goes well beyond Nigeria."

At least 1.5 million people have been forced to flee their homes in northeast Nigeria and in neighboring Cameroon, Niger and Chad since May 2013 as Boko Haram stepped up its insurgency.

The United Nations is scaling up operations in Nigeria and neighboring countries to address the humanitarian crisis triggered by the Boko Haram offensive, Chambas said.

The envoy voiced hope that the new Nigerian leadership "will remain committed to the sub-regional fight against Boko Haram".

UN deputy aid official Kyung-wha Kang said the situation in northeast Nigeria and affected areas in neighboring countries was "dire," with the violence having a "devastating impact" on women, children and young people.