United Nations Secretary-General Ban Ki-moon is urging Iraqi leaders to address the root causes for a surge of bloodshed in the country.

Al-Qaida-linked militants have seized control of two key cities while violence between minority Sunnis and the Shi'ite-led government has killed thousands over the last nine months.

Mr. Ban made an unannounced visit to Baghdad Monday for talks with Prime Minister Nouri al-Maliki. The U.N. chief said he is especially worried about deteriorating security in Iraq and is deeply saddened by the deaths of innocent Iraqis.

Mr. Ban said the Iraqi people are looking to their leaders for what he called "tangible benefits" and a "better future." He said it is important for all political leaders to unite against terrorism and stabilize the situation.

Prime Minister Maliki told the Reuters news agency there will be "no limit" in recruiting fighters to help drive al-Qaida out of the cities of Fallujah and Ramadi. This includes Sunni tribesmen who reject extremism. Mr. Maliki said they contribute to security and the government has to take care of them.

The prime minister promised salaries and full benefits to any tribesmen who fight alongside the army against al-Qaida.

Four separate car bombs killed at least 25 people Monday in Baghdad.

Iraqi officials blame their country's slide back into violence in part on Syria's civil war, which has fueled sectarian tensions and instability across the region.