BAGHDAD — U.S. Defense Secretary Robert Gates flew to Iraq today to begin the second leg of his tour of two major war zones.

Gates' visit to Iraq comes during a week in which coordinated Baghdad bombings have killed 127 people and wounded more than 500. Al-Qaida's umbrella group in Iraq claimed responsibility today for the bombings and warned of more strikes to come against the Iraqi government.

Pentagon spokesman Geoff Morrell called the bombings "heinous" and said they were a sign of desperation by insurgents.

The U.S. military has warned that insurgents would probably continue high-profile attacks in an attempt to destabilize the Iraqi government in advance of March 7 parliamentary elections.

Gates' agenda in Baghdad includes meetings with Iraqi Prime Minister Nouri al-Maliki and President Jalal Talabani.

The defense secretary flew to Iraq from Kabul after wrapping up a three-day visit in Afghanistan, where he met with U.S. troops and Afghan leaders, including President Hamid Karzai.