American troops killed four suspected insurgents and captured nine others during an operation that followed the alleged leader of a suicide-bombing network in Diyala province, north of Baghdad.

According to information released Thursday, the operation was put into play by tips and confessions gathered from detainees who had been previously captured. The information led the troops to watch and follow a suspected leader of the bombing network, who traveled to an area north of Baqouba, the Diyala provincial capital.

"The area was believed to be a hide-out location used to house weapons," a news release read. "The house was rigged with booby-traps throughout."

U.S. troops called in airstrikes, "which triggered several secondary explosions, indicating bomb materials and weapons on the ground."Four people were killed in the strikes, officials said.

When troops on the ground went to inspect the area, they found a tunnel network, fighting positions, weapons and documents related to insurgent operations.

U.S. officials said the group was al-Qaida in Iraq, the Sunni group whose members have largely been pushed out of major cities and into areas like Diyala province and north.

Those captured in the operation included alleged operatives who had fled to Tikrit and Mosul.

Though most of the attention in recent months has focused on Shiite militias operating in Baghdad and areas further south, U.S. officials continue their push against Sunni groups as well. In interviews in recent weeks, the No. 2 commander of U.S. troops in Iraq has called al-Qaida in Iraq the top danger in the country.

"AQI remains the most dangerous threat out there for us," Lt. Gen. Lloyd J. Austin III told The Washington Post recently. "We have had significant effects on them. But they are not defeated."

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