BAGHDAD, Iraq – Car bombs exploded in quick succession yesterday near four Christian churches and the office of the Vatican envoy, killing three people and raising new concerns about sectarian tensions. At least 17 other people were killed in other violence around the country.

No group claimed responsibility for the bombings, which occurred within a half hour near two churches in Baghdad and two in Kirkuk,180 miles to the north. The fifth bomb exploded about 50 yards from the Vatican mission in the capital.

Suspicion fell on Islamic extremists such as Al Qaeda in Iraq – led by Jordanian-born terrorist Abu Musab al-Zarqawi – that have been responsible for massive car bombings and suicide attacks against Iraqi Shiite civilians.

Meanwhile, an ABC News co-anchor, Bob Woodruff, and cameraman, Doug Vogt, were seriously injured yesterday when the Iraqi army vehicle they were traveling in was hit by a roadside bomb and small arms fire near Taji, about 12 miles north of Baghdad.

Both suffered serious head injuries and underwent surgery at an American military hospital in Balad, ABC News said.

The American military announced the death of an American soldier in a roadside bomb blast in Baghdad on Saturday. At least 2,241 American military personnel have died since the war began, according to an Associated Press count.

The attacks on Christian sites came at a time of rising sectarian tensions, including reprisal killings and raids, that threaten to complicate efforts to form a broad-based government following the December 15 parliamentary elections.

“This was a reaction from the al-Zarqawi people against Christians who they believe support the U.S. military in Iraq,” a senior Shiite lawmaker, Ali al-Adeeb, said. “Such acts are rejected by Shiites and Sunnis alike who have been living together with our Christian brothers in Iraq throughout history.”

A prominent Sunni Arab politician, Naseer al-Ani, called the bombings “terrorist acts.”

Three people died in the bombing at the Church of the Virgin in Kirkuk, police said. At least nine people were injured in the bombings, which caused little damage to the Christian buildings.

Despite the relatively low casualty toll, the bombings are expected to raise fears among the country’s small Christian minority – about 3% of Iraq’s 27 million people. At least 12 people were killed in a series of church bombings in 2004.

Vatican officials had no comment.

American officials are pressing the Iraqis to agree on a government that can win the trust of the Sunni Arabs, the minority community that forms the backbone of the insurgency. Such a government is considered essential if America and its international partners are to begin bringing their troops home this year.

However, neither the majority Shiites nor the minority Sunnis appear ready for major concessions in coalition talks. Yesterday, a key Sunni Arab politician accused Shiite-led security forces of pursuing a strategy of sectarian “cleansing” in Baghdad.

“Mosques and houses are empty because clerics and ordinary men are being chased as if there was a sectarian cleansing in Baghdad,” Adnan al-Dulaimi told reporters. “Violence only breeds more violence. I demand that this sectarian sedition be stopped.”

Mr. al-Dulaimi, leader of the main Sunni bloc in the next parliament, also said he would oppose awarding the vital interior and defense ministries, which control state security forces, to Shiite religious parties.

Mr. al-Dulaimi’s comments followed a series of raids last week by Interior Ministry commandos into majority Sunni Arab neighborhoods in the capital. The government insists the raids are directed against insurgents who have targeted Shiite civilians as well as American and Iraqi soldiers and police.

On Saturday, the head of the Badr Brigade Shiite militia said Shiite religious parties will “never surrender” the interior and defense ministries. An alliance of Shiite parties won 128 of the 275 parliament seats last month – the largest single bloc.

Yesterday, bombings and ambushes killed eight policemen and a medic in attacks across Baghdad and in the northern cities of Baqouba and Beiji.

A massive car bomb killed four Iraqi soldiers and wounded six more in Saddam Hussein’s birthplace of Uja, about 75 miles north of Baghdad. It was unclear whether the attack was linked to Saddam’s trial, which resumed yesterday.

A former high-ranking general in Saddam’s disbanded army, Lieutenant General Mahmoud Idham, was assassinated near Tikrit, 80 miles north of Baghdad, police said. The motive for the attack was unclear.

American soldiers shot dead three men wearing Iraqi police uniforms and captured a fourth during a gunfight in Kirkuk. No police identity cards were found, and Iraqi police Brigadier Serhad Qadir said they were suspected insurgents disguised as policemen.