Iraq's national security advisor says authorities have arrested a key al-Qaida suspect in connection with the bombing of a Shi'ite shrine that triggered sectarian violence earlier this year.

Mowaffaq al-Rubaie said in Baghdad Wednesday that the Tunisian suspect, known as Abu Qudama, was wounded in a clash with Iraqi and U.S. troops a few days ago.

He said the man confessed to bombing the centuries old Golden Dome shrine in Samarra on February 22. But Rubaie said the suspected ring-leader of the plot, Haitham al-Badri, is still on the run.

In new violence, a car bomb killed three people near a Sunni mosque northeast of Baghdad. A roadside bomb killed another Iraqi near the capital. The U.S. military also said an American soldier and a Marine were killed in separate attacks Tuesday.

In another development, Iraqi Prime Minister Nouri al-Maliki said Wednesday several insurgent groups have contacted him to discuss amnesty as part of his national reconciliation plan.

He added that militants involved in the killing of U.S.-led troops will not be eligible.

On Tuesday in Washington, the U.S. general in charge of training Iraq's new security forces, Lieutenant General Martin Dempsey, said the new Iraqi army will be fully in place by the end of the year

But he said the Iraqi army, police and the ministries that support them will need additional time to function effectively for the country to not need foreign forces.

Some information for this report was provided by AFP, AP and Reuters.