BAGHDAD (AP) _ A suicide bomber wearing a hidden belt of explosives attacked a police station in Iraq's volatile province of Diyala on Wednesday, killing at least four policeman just days after a double suicide bombing in the same province left nine U.S. soldiers dead.
Wednesday's explosion, which also injured at least 16 people, occurred at the front gate of the police station in a marketplace in Balad Ruz city, 45 miles northeast of Baghdad, police said. All fatalities were policemen and the wounded included 11 civilians and five policemen, authorities said.
Since U.S. and Iraqi troops launched the security crackdown in Baghdad in February, Sunni militants are believed to have moved out of the Iraqi capital to seek haven in nearby areas such as Diyala.
Despite that, a U.N. report released Wednesday said that violence in Baghdad remains at high levels.
In its first human rights report since the security plan was launched on Feb. 14 _ with increasing U.S. and Iraqi troops levels in the capital _ the U.N. Assistance Mission for Iraq (UNAMI) said civilian casualties in the daily violence between January and March remained high, concentrated in and around Baghdad.
UNAMI also said that for the first time since it began issuing quarterly reports on the human rights situation in Iraq, the new Jan. 1 through March 31 report did not contain overall death figures from Iraq's Ministry of Health because it refused to release them.
The U.N. agency said the reason appeared to be that after the publication of its last human rights report on Jan. 16, Prime Minister Nouri al-Maliki's office told UNAMI its mortality figures were exaggerated, ``although they were in fact official figures compiled and provided by a government ministry.''
``UNAMI emphasizes again the utmost need for the Iraqi government to operate in a transparent manner, and does not accept the government's suggestion that UNAMI used the (previous) mortality figures in an inappropriate fashion,'' the report said.
The current report cites many examples of deadly attacks by insurgents and militias across Iraq during the first three months of the year, but it often relies on media accounts of such killings and does not provide overall numbers for the period.
In other violence Wednesday, a roadside bomb hit a U.S. military convoy in Baiyaa, a mixed Sunni-Shiite area of southwest Baghdad, setting fire to one of its Humvees, police said.
AP Television news footage from the scene showed flames and smoke rising from a Humvee on a two-lane road, which was closed off by at least one other Humvee and a U.S. tank. It was not immediately known if the attack caused any casualties.
Despite Baghdad's violence, radical Shiite cleric Muqtada al-Sadr strongly condemned construction of a wall around a Sunni neighborhood in the capital, calling for demonstrations against the plan as a sign of ``the evil will'' of American ``occupiers.''
The remarks, in a statement read by an aide, were the first by the anti-American cleric since the U.S. military announced last week that it was building a three-mile long, 12-foot-high concrete wall in Azamiyah, a Sunni stronghold that has been targeted by mortar and rocket attacks by Shiite militiamen.
Many Sunnis also have protested the plan.
On Tuesday, an al-Qaida-linked group claimed that it used ``new methods'' in staging Monday a double suicide bombing with dump trucks that blasted a paratrooper outpost in Diyala province, killing nine Americans from the 82nd Airborne Division and wounding 20.
The attack underscored the ability of guerrillas of the Sunni Arab-dominated insurgency to wage war in Iraq four years after the U.S.-led invasion, and it came in a region that has seen violence escalate since U.S. and Iraqi troops launched the security crackdown in Baghdad.
The first truck hit outlying concrete barriers surrounding the outpost at Sadah and exploded after soldiers opened fire. A second truck rammed into the wrecked vehicles, dragging it and other rubble before it exploded 30 yards from the building housing the post's troops, said Lt. Col. Michael Donnelly, U.S. military spokesman in north Iraq.
Neither vehicle penetrated the patrol base's inner perimeter, but the second powerful blast ruptured the wall of the building, collapsing its second floor and causing most of the soldier casualties, a U.S. military statement said Wednesday. A civilian house was destroyed and several smaller structures collapsed in a nearby neighborhood, the military said. A civilian hospital and a mosque about 200 yards from the patrol base also were damaged.
All the casualties were in the 5th Squadron, 73rd Cavalry Regiment, 3rd Brigade Combat Team, which has been conducting operations in largely impoverished villages in the area as part of a security push to tame insurgent activity in Diyala.
The deaths made April the deadliest month of the year for the U.S. military. It was also the single deadliest attack on U.S. ground forces since Dec. 1, 2005, when 10 Marines were killed by a bomb inside an abandoned flour mill near Fallujah.
Donnelly said the patrol base was set up less than a month ago after an operation that sought to drive militants from the area. Sadah, a rural Sunni town of about 7,000 people near the capital of Diyala province, Baqouba, has been an al-Qaida stronghold.
The Islamic State of Iraq, an umbrella group of Sunni militants that includes al-Qaida in Iraq, said it was behind the suicide attack. Its account on the Internet was similar to that of the U.S. military, but claimed it used new techniques.
``Almighty God has guided the soldiers of the Islamic State of Iraq to new methods of explosions,'' the statement said without elaborating, while claiming 30 Americans died.