Iraq's Sunni deputy prime minister was wounded Friday in a homicide bombing near the heavily fortified Green Zone that killed as many as, authorities said.

The bomber blew himself up as Salam al-Zubaie, one of two deputies to Prime Minister Nouri al-Maliki, and other worshippers were leaving a mosque in the courtyard of his house, according to police and a Sunni politician.

Military spokesman Lt. Col. Christopher Garver said al-Zubaie was in a hospital run by the U.S. in the Green Zone but would not comment on his condition.

Ziad al-Ani, a top official of the Sunni Iraqi Islamic Party, said al-Zubaie was slightly wounded in his leg and was taken to the hospital for treatment.

Police said six people were killed, including an adviser, and 10 others were wounded, including five of al-Zubaie's bodyguards. The adviser, Mufeed Abdul-Zahra, was wounded in the attack and died later at the hospital.

There were conflicting accounts about the exact timing of the attack. Police said it occurred as worshippers were leaving, while al-Ani said the bomber blew himself up inside the mosque during the traditional weekly prayer service.

Baghdad authorities have imposed a weekly four-hour vehicle ban on Fridays to protect the services from homicide car bombers.

The mosque was built inside the courtyard of al-Zubaie's compound in a residential area behind the Foreign Ministry, but worshippers can access it from the street outside, al-Ani said. The compound is near the Green Zone, which houses the U.S. and British embassies and the Iraqi government headquarters.

The attack came a day after a rocket landed in the Green Zone as U.N. Secretary-General Ban Ki-Moon and al-Maliki were holding a joint press conference.

Meanwhile, an Al Qaeda umbrella group in Iraq purportedly denied Friday that chlorine was used in recent bombings in Anbar province but warned that it would target all tribes and politicians supporting U.S. efforts in Iraq.

The statement came a day after a rocket exploded 50 yards from the U.N. Secretary-General Ban Ki-moon during a news conference in Baghdad's Green Zone, causing him to cringe and duck just minutes after Iraq's prime minister said the visit showed the city was "on the road to stability."

The Katyusha rocket was fired from a mainly Shiite area on the east bank of the Tigris River, not far from The Associated Press office. The heavily guarded Green Zone on the opposite bank is home to the U.S. Embassy, Iraq's government and the parliament.

Iraq's Shiite-dominated government has been quietly pushing for a greater U.N. role and was banking on decreased violence in the capital to show that it was returning to normal six weeks into a joint security crackdown with American forces.

"We consider it a positive message to (the) world in which you confirm that Baghdad has returned to playing host to important world figures because it has made huge strides on the road toward stability," Prime Minister Nouri al-Maliki told Ban moments before the rocket attack.

Ban's unannounced stop in the Iraqi capital Thursday was the first visit by a U.N. secretary-general since Kofi Annan, his predecessor, came to Baghdad in November 2005. The U.N. Security Council issued a statement strongly condemning the rocket firing as an "abhorrent terrorist attack."

The United States has sent about 30,000 additional troops to support the efforts to pacify the capital, as well as Anbar.

A roadside bomb killed a U.S. soldier Thursday in western Baghdad, raising to at least 3,228 members of the U.S. military have died since the Iraq war started in March 2003, according to an Associated Press count.

While the fighting in Baghdad has been between Shiites and Sunnis, it has been more of an internal struggle in the Sunni-dominated province that stretches west of the capital to the borders with Syria, Saudi Arabia and Jordan.

The U.S. military said three homicide bombers driving trucks rigged with tanks of toxic chlorine gas struck targets in the Sunni insurgent stronghold west of Baghdad last week, killing at least two Iraqi policemen and sickening 356 people.

The three bombings, which bore the hallmarks of Sunni insurgents, raised to seven the number of chlorine attacks launched since Jan. 28, causing the U.S. military to warn that insurgents are adopting new tactics in a campaign to spread panic.

The Islamic State of Iraq, which groups Al Qaeda in Iraq and several other Sunni extremist groups, said its duty was to "purify these tribes from those outlaws" who support the U.S.-backed government. But it denied using "poisonous gas" against civilians, calling the chlorine claims propaganda.

"There are some people who choose to be helpers to the crusader occupiers and their stooges, those who try to save the crusaders and they were the last card used by the U.S. army in its war against the true mujahedeen (holy fighters)," the group said in an Internet statement. The statement could not be independently verified, but it was posted on a Web site commonly used by militant groups.

The group said it was targeting members of the Albu Issa tribe who had recently denounced Al Qaeda in a March 20 raid on a police station in Amiriyah, east of Fallujah.

The military said the chlorine attacks occurred on March 16 in Amiriyah and two other areas, and it was not clear if the militant statement was referring to those or clashes that broke out on Tuesday in Amiriyah and Ramadi.

It said "35 apostate policemen were killed and four pickups were seized," in the attack, adding that "this is against what was mentioned by some satellite channels that the people were targeted by poisonous gas."

The statement also singled out Iraq's Sunni Deputy Prime Minister Salam al-Zubaie and Sunni Vice President Tariq al-Hashemi, as well as the Anbar Salvation Council, an alliance of clans in the province backing the government.

"We tell our people from the tribes and tribal leaders not to help the crusade occupier and its tails and do not allow your sons to join and become tools used by crusaders to fight the mujahedeen," it said. "We tell the rest of the agents and stooges who have joined the crusaders and the "council of Anbar infidels" that their fate will be the same of those killed in Amiriyah."

A video posted on the Internet Thursday also showed Abu Yahia al-Libi, an Al Qaeda militant who escaped from a U.S. prison in Afghanistan, urging Sunni militants in Iraq to join the terror group and claiming the U.S. military's security plan for Baghdad has failed.

The chief of police in the southern city of Basra, meanwhile, said a curfew imposed following clashes between Shiite militiamen loyal to radical cleric Muqtada al-Sadr and guards outside the headquarters of the rival Shiite Fadhila party has been lifted.

The militiamen captured eight Fadhila members before the building caught fire and 12 Mahdi Army fighters were wounded in the gunbattle, police said, adding that clashes also had erupted between the two sides near the residence of Basra's Fadhila governor Mohammed al-Waeli.

Police Chief Gen. Mohammed al-Moussawi said the curfew was lifted Friday morning and agreement had been reached for the detainees to be released.

In violence Friday, police found three bullet-riddled bodies, including two women, in Diwaniyah, 80 miles south of Baghdad, including two women a Shiite city that has seen recent clashes between militiamen and police.

The Associated Press contributed to this report.