U.S. concerned by Nigerian threats WASHINGTON, June 4 (UPI) -- U.S. citizens are advised to avoid travel to parts of Nigeria because of a looming terror threat and state of emergency, the State Department said. Nigerian President Goodluck Jonathan in May declared a state of emergency in northern Borno, Yobe and Adamawa states. Jonathan, a Christian, said Islamic militants had taken over parts of Borno. Militant action in the Muslim north amounted to a declaration of war, he said. The U.S. State Department said it was "severely limited" in how it could respond to any U.S. citizen in those states. Travel for employees at the U.S. Embassy in Nairobi to the three northern states is restricted. "U.S. citizens should be aware that extremists could expand their operations beyond northern Nigeria to the country's middle and southern states," the State Department said Monday. The warning expressed concern about the activity of Boko Haram and Ansura, an offshoot of the militant group. Ansura took credit for the execution of seven foreign nationals in Nigeria earlier this year. The State Department announced Monday it was offering as much as $5 million each for information that would lead authorities to the leaders of al-Qaida in the Islamic Maghreb, the Movement for Unity and Jihad in West Africa, and Boko Haram. The United Nations estimates about 200 people were killed and more than 2,000 houses were destroyed in a recent Nigerian military raid in the north. The raids were allegedly in response to an attack by Boko Haram.