The United States on Wednesday blacklisted Nigeria’s Boko Haram group and an offshoot known as Ansaru as terror groups, bowing to months of pressure to move against the brutal insurgents.

The United States on Wednesday blacklisted Nigeria's Boko Haram group and an offshoot known as Ansaru as terror groups, bowing to months of pressure to move against the brutal insurgents.

"These designations are an important and appropriate step, but only one tool in what must be a comprehensive approach by the Nigerian government to counter these groups ... to help root out violent extremism," the State Department said in a statement.

US accused Boko Haram of claiming thousands of lives since 2009 mainly in Nigeria.

"In the last several years, Boko Haram and Ansaru have been responsible for thousands of deaths in northeast and central Nigeria," key White House homeland security advisor Lisa Monaco said in a statement.

US officials also accuse Boko Haram of links to Al-Qaeda in the Islamic Maghreb, while Ansaru is a splinter faction that earlier this year kidnapped and executed seven foreign construction workers.