BAGHDAD (AP) – Gunmen in two cars attacked a minibus heading to Baghdad from a Shiite town north of the capital Monday, killing seven passengers, including a child, police said.

A mortar shell hit the roof of the parliament building inside the heavily guarded Green Zone in Baghdad, but no one was injured, a lawmaker said.

Thousands of soldiers, meanwhile, continued combing through fields and questioning suspects as the search for three missing American soldiers continued following a May 12 ambush south of Baghdad that killed four other soldiers and their interpreter.

The minibus, which left the town of Khalis, was driving near the violence-wracked city of Baqouba, 35 miles northeast of Baghdad, when it was ambushed outside the town of Hibhib, police said.

The attack underscored the sectarian violence and instability that continues to plague Diyala province north of Baghdad despite the three-month-old security crackdown in Baghdad and surrounding areas.

In western Baghdad, a roadside bomb exploded near a group of Iraqi soldiers patrolling the Sunni-dominated Adil neighborhood in western Baghdad, killing three of the soldiers and injuring two.

In the confusion of the attack, the soldiers fired near the office of Adnan al-Dulaimi, the leader of parliament’s largest Sunni Arab bloc, the Iraqi Accordance Front, according to his office. No one was injured.

The stepped-up American and Iraqi patrols of the capital during the crackdown have left the troops more vulnerable to attack by insurgents, military officials say.

The American military reported Sunday that six American soldiers on patrol in Baghdad were killed in a roadside bombing along with their interpreter on Saturday. A seventh soldier died in a blast Saturday in Diwaniya, a mostly Shiite city 80 miles south of the capital, where radical Shiite militias operate.

Those deaths brought the number of American troops killed in Iraq since Friday to at least 15 – eight of them in Baghdad. So far, at least 71 American troops have died in Iraq this month – most of them from bombs.

The mortar shell that hit parliament landed almost above the office of the parliament speaker and caused only minor damage, said lawmaker Sabah al-Saadi, who was at a committee meeting inside at the time.

A few hours later, several more mortar rounds were fired. Some of them landed in the Green Zone, but there were no reports of casualties, the American Embassy said.

An April 12 suicide bombing in the parliament’s dining hall killed one lawmaker.

The blast was part of a sharp increase in recent weeks of mortar attacks on the Green Zone, which also houses other Iraqi government offices and the American Embassy. The compound, on the banks of the Tigris River, is surrounded by cement walls and patrolled by U.S. and Iraqi soldiers, as well as private security guards.

Amid the almost daily mortar barrages, people living inside have questioned whether it is truly safe to remain there.

Journalists have also been targeted by the violence, and the Iraqi newspaper Azzaman reported Monday that one of its reporters, Ali Khalil, 22, was kidnapped while leaving a relative’s house in the increasingly volatile Baiyaa neighborhood of Baghdad and found dead several hours later. Khalil was survived by his wife and 1-week-old baby, the newspaper said.

The attack came three days after two Iraqi journalists working for ABC News were ambushed and killed on their way home from work. The New York-based Committee to Protect Journalists said 104 journalists – not including Khalil – have been killed since the 2003 American-led invasion of Iraq. About 80 percent of the journalists killed were Iraqi, according to CPJ.

In other violence Monday, two gunmen killed two police officers as they walked by the police station in Muqdadiyah, about 60 miles north of Baghdad.

Insurgents also fired mortar rounds into a bank in Baqouba as customers were waiting in line to collect their pensions, killing two people, police said.

Violence also hit the southern city of Basra, with gunmen killing one police officer and wounding another in an attack on their patrol, police said. Police also reported that the chief of customs in Basra, Col. Khalaf al-Badran, escaped injury when a roadside bomb struck his convoy as it left the airport. And a fuel tanker was damaged when it was hit by a roadside bomb, police said.

Two Republican senators said Sunday at an international conference hosted by the Geneva-based World Economic Forum in Jordan that America has evidence Iran sent weapons and trainers to instruct militants in Iraq to carry out terror attacks.

Senator Hatch of Utah told a panel discussion on Iraq’s future that during a trip last week to Iraq, he saw “evidence that Iran was supplying weapons and bomb-making components to Iraqi terrorists.”

A former Iranian government official, who was on the same panel, denied the claims.

“Iraq is already so full of arms that it doesn’t need arms from Iran,” said hard-liner Mohammed J.A. Larijani, a former deputy foreign minister and brother to Iran’s top nuclear negotiator, Ali Larijani.

But Senator Smith of Oregon told the panel he saw “confiscated Iranian weapons” and captured Iranians who confessed to a mission to train Iraqi extremists.