The United States is assisting the Nigerian government to find and free some 200 schoolgirls abducted by militants, the White House said on Monday. U.S. assistance to Nigeria focuses on information-sharing and improving Nigeria's forensics and investigative capacity, White House spokesman Jay Carney told a press briefing, adding that "we view what has happened there as an outrage and a terrible tragedy. " Carney said President Barack Obama has been briefed several times on the issue and his national security team is monitoring the situation closely. About 200 girls from Chibok community in northeastern Nigeria's Borno State were abducted in April. On Monday, militant group Boko Haram claimed responsibility for the act and threatened to sell the girls. "Boko Haram is a terrorist organization with heinous and malicious intent," Carney said. At a press briefing on Monday, State Department spokeswoman Marie Harf said information that U.S. has indicates that many of the girls have likely been moved out of the country to neighboring countries. In November, U.S. blacklisted Boko Haram as a terrorist organization and slapped sanctions on it, including denied access to U.S. financial institutions, a freezing on its assets in U.S. banks and a ban on doing business with or providing support to it.