Baghdad, Iraq ? Iraq has issued arrest warrants against the defense minister and 27 other officials from the U.S.-backed government of former Prime Minister Iyad Allawi over the alleged disappearance or misappropriation of $1 billion in military procurement funds, officials said Monday.

Those accused include four other ministers from Allawi’s government, which was replaced by an elected Cabinet led by Shiite parties in April, said Ali al-Lami of Iraq’s Integrity Commission. Many of the officials are believed to have left Iraq, including Hazem Shaalan, the former defense minister who moved to Jordan shortly after the new government was installed.

For months, Iraqi investigators have been looking into allegations that millions of dollars were spent on overpriced deals for shoddy weapons and military hardware, apparently to launder cash, at a time when Iraq was battling a bloody insurgency that still persists.

In Baghdad, a suicide bomber detonated a car full of mortars near an entrance to the fortified Green Zone on Monday, killing a U.S. soldier and six Iraqis in one of a string of insurgent attacks in which at least 13 other Iraqis also died.

Gunmen opened fire on a convoy carrying delegates from the Arab League in Baghdad during the organization’s first visit to Iraq since the fall of Saddam Hussein. The league has met resistance from Shiite and Kurdish leaders as it tries to piece together a reconciliation conference with Sunnis. A policeman was wounded in the shooting, but no one in the delegation was hurt.

An Iraqi man looks at a copy of the country's new constitution at a distribution center Monday in Najaf, Iraq. Shiite and Kurdish officials continued to negotiate with Sunni Arab leaders over last-minute additions to the constitution, trying to win Sunni support ahead of next weekend's referendum. U.S. officials were acting as mediators.

The violence comes five days ahead of Iraq’s key vote on a new constitution, which Kurds and the majority Shiites largely support and the Sunni Arab minority rejects. Sunnis are campaigning to defeat the charter at the polls, though officials from all sides have been trying up to the last minute to decide on changes to the constitution to swing Sunni support.

Whether the constitution passes or fails, Iraq is due to hold elections for a new parliament on Dec. 15. The corruption allegations are a blow to Allawi as he tries to assemble a coalition of moderates to run against the current ruling Shiite-led coalition in the election in a bid to get back into the government.

With strong U.S. backing, Allawi was named head of the first transitional government after the U.S. returned sovereignty to Iraq in June 2004, but his Iraqi List party did poorly in January parliamentary elections that swept the Shiite-Kurdish coalition into power.

Besides Shaalan, warrants were issued against Allawi’s labor, transportation, electricity and housing ministers, as well as 23 former Defense Ministry officials, said al-Lami, who heads Iraq’s De-Baathification Commission, part of the Commission of Public Integrity.