A bus filled with Shiite pilgrims collided with a British military vehicle in southern Iraq, killing seven pilgrims and injuring 27 others, Iraqi and British officials said Wednesday.

The pilgrims were coming from the Shiite holy city of Karbala when the accident occurred late Tuesday on the outskirts of Basra, said Maj. Gen. Mohammed Jawad Huwaidi, the top Iraqi military official in Basra.

The British Defense Ministry said the armored vehicle was on a routine night patrol and was parked when the bus drove into the back of it. The ministry statement said seven civilians were killed and several others were injured.

Hundreds of thousands of Shiite pilgrims converged on Karbala last week to celebrate the end of 40 days of mourning that follow the anniversary of the seventh-century death of one of Shiite Islam's most revered saints, the Prophet Muhammad's grandson Hussein. Many of the pilgrims began their trip home Monday.

More than 60 pilgrims were killed in attacks as they made their way to and from Karbala. Violence in Iraq has declined to a five-year low, but periodic attacks continue throughout the country.

A roadside bomb targeting a police patrol in the northern city of Mosul killed one policeman Wednesday, said a police official, speaking on condition of anonymity because he was not authorized to talk to the press.

In Baghdad, gunmen killed a local official from the Sunni Iraqi Islamic Party, said police and medical officials, speaking on condition of anonymity for the same reason. The party is Iraq's largest Sunni group, and several of its officials serve in top national government posts.

The U.S. military said Wednesday it is working to transfer security of two key oil platforms in southern Iraq to Iraqi forces. The platforms are responsible for exporting up to 75 percent of Iraq's oil, said the military statement.

A U.S.-Iraqi security agreement that came into force Jan. 1 requires that all American troops withdraw from Iraq by the end of 2011.

The Iraqi navy is currently working with U.S. and British forces to protect the platforms. Iraq is expected to take over full responsibility for security at the Khor al-Amaya terminal by the end of the year, said the U.S. military. It is scheduled to take over a portion of the security of the much larger Basra terminal by that time as well.

As Iraq takes over greater responsibility for security in the country, the government hopes political progress will help reinforce growing stability. Iraq held provincial elections throughout much of the country on Jan. 31, and the U.S. hailed the voting for the absence of violence.

But politics at the national level has been hampered by parliament's inability to choose a new speaker.

The Sunni speaker, Mahmoud al-Mashhadani, resigned in December after widespread complaints about his erratic behavior. Under a power-sharing formula between the country's main ethnic and religious groups, his replacement must be a Sunni Arab. But parliament's main Sunni bloc, the Iraqi Accordance Front, has been unable to agree on a candidate.

As a result, parliament held a secret vote Wednesday in an attempt to choose a candidate from five potential choices, Hassan al-Rubaie, a senior lawmaker loyal to Shiite leader Muqtada al-Sadr, told The Associated Press.

None of the candidates received a majority, but the vote narrowed down the choices to Ayad al-Sammaraie, a senior member of the Iraqi Islamic Party, and Khalil Jadoua, a member of the National Dialogue Council, according to al-Rubaie.

A second round of voting will be held Thursday to choose between the two candidates, said al-Rubaie.

Tension over the previous speaker, al-Mashhadani, came to a head in December during a shouting match in parliament over the detention of journalist Muntadhar al-Zeidi, who threw his shoes at former President George W. Bush at a news conference in Baghdad.

Al-Zeidi has been in custody since the Dec. 14 news conference and is scheduled to go on trial Thursday on charges of assaulting a foreign leader.

Dozens of people demonstrated in Baghdad on Wednesday demanding al-Zeidi's release. They carried banners reading, "We demand the release of the true son of Iraq" and "Al-Zeidi's act is appreciated by all the honest people in the world."

Al-Zeidi's brother, Durgham, attended the protest and said about 50 of the journalist's relatives will attend Thursday's trial.

"We have fears that this case will be politicized," said al-Zeidi's brother. "We are worried that the Iraqi government will impose the kind of sentence that appeals to the Americans."