BAGHDAD, Iraq — British and Australian forces handed over security duties for a relatively peaceful southern province to Iraqis on Thursday in the first such transfer of an entire province. At least 18 people were killed in attacks nationwide, however, illustrating the security challenge the country still faces.

Prime Minister Nouri al-Maliki hailed the security transfer in Muthanna province as an important step toward the goal of full Iraqi responsibility for all 18 provinces by the end of next year.

"It is a great national day that will be registered in the history of Iraq. This step will bring happiness to all Iraqis," al-Maliki said during a handover ceremony in the provincial capital of Samawah. "Be sure that the terrorists want to destroy and foil the process of taking over the security issue and to hamper the political process and the national unity government."

British Defense Secretary Des Browne said the move puts the Iraqis "one step nearer to assuming full responsibility for their own security and to building a stable and democratic future for their country."