Gates arrives in Kabul for unannounced visit

KABUL, Afghanistan (CNN) -- U.S. Defense Secretary Robert Gates arrived in Afghanistan on Monday for his third visit to the war-torn nation since being confirmed as Pentagon chief.

Gates is expected to speak with military commanders on Tuesday. He will later brief reporters with his Afghan counterpart, Abdul Rahim Wardak, and Afghan President Hamid Karzai.

Gates arrived from the East African nation of Djibouti, where he completed his first visit to the Horn of Africa since becoming defense secretary.

He visited Combined Joint Task Force Horn of Africa, a command center for humanitarian efforts in the region.

Talks between Gates and Djiboutian officials centered on how the the task force will operate in the Pentagon's new African Command. The region contains "real or potential flashpoints" on the continent and "ungoverned areas where terrorists driven from Afghanistan might seek refuge."

Gates' visit also comes amid violence in southern Afghanistan.

On Monday, a suicide bomber blew himself up near a police checkpoint in Nimruz province, killing four and wounding seven, Afghan authorities said.

On Sunday, coalition troops killed "several militants," including one believed to be involved in the kidnapping of an Italian journalist, the U.S.-led coalition said.

The incident Sunday took place in Helmand province, where troops were targeting Taliban command and control networks.

The military said troops "conducted a precision-guided munitions strike targeting a senior Taliban commander believed to be involved in the March kidnapping of Italian journalist Daniele Mastrogiacomo, his interpreter and his driver."

There were no indications of casualties to civilians "not taking part in hostilities."

Mastrogiacomo, a correspondent for the Italian daily La Repubblica, was taken captive in Helmand province on March 5 by the Taliban and and then released two weeks later.

Italian Prime Minister Romano Prodi negotiated a deal with Karzai to have Mastrogiacomo freed in return for the release of five Taliban prisoners in Afghan custody. E-mail to a friend

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