Boko Haram insurgents attacked the outskirts of Borno state capital Maiduguri in Nigeria on Saturday morning and at least 11 people were killed in the fighting, residents and security sources said.

The attack occurred barely a day after the inauguration of President Muhammadu Buhari, who swore to crush the Islamist militant group and move the command center for military operations away from the capital Abuja to Maiduguri.

Gunshots from high-caliber weapons could be heard between about 1 a.m. and 2:20 a.m. (8 p.m. -9.20 p.m. EDT) from the southwestern part of the city.

A military source said the shooting took place around the Damboa road near the small settlement of Mule, about 10 km (6 miles) from Maiduguri, a city of two million people.

"A rocket launcher from Boko Haram hit a house around the Bulumkutu area...and killed five people. Our boys also picked up six corpses in different locations," local militia member Mohammed Bunu said.

The militants tried to cross trenches dug around the city, he said.

The attack follows twin bomb blasts early on Friday in Tashan Alade, a remote Borno town, which killed at least seven people.

Thousands have been killed and about 1.5 million displaced during Boko Haram's six-year-old insurgency to carve out a state adhering to strict Islamic law in Nigeria, Africa's biggest economy and top oil producer. At the start of the year it controlled a swathe of territory larger than Belgium in the northeast of the country.

Boko Haram has since been pushed back with the help of offensives launched by troops from Chad and Niger while Cameroon has fought them off along its borders.

The United States and Britain said on Friday they were ready to increase military cooperation with Nigeria to defeat Boko Haram.

(Reporting By Lanre Ola, Writing by Julia Payne; Editing by Angus MacSwan)