The explosion shortly after 9 a.m. destroyed several vehicles, sent up a huge cloud of black smoke, and was followed by militants firing machine guns at security forces. It also underscored the difficulties U.S. and Iraqi authorities face in curbing the rampant insurgency.
U.S. soldiers captured four wanted militants in a number of separate raids since Monday, including a former spy in Saddam Hussein's secret service believed to be financing several terrorist groups in western Baghdad's Ghazaliyah district, the military said.
The former spy, whose identity was not revealed, also was suspected of working as a cameraman for a terrorist group, apparently filming attacks on coalition forces that later were posted on Internet sites or distributed to the media.
In other recent developments:
Iraqi authorities are trying to take the fight to insurgents, who have launched attacks that have killed at least 765 people, including U.S. troops, since the new government was announced April 28, according to an Associated Press count. Many of the killings have come as a result of suicide bombings, with about 100 attacks being carried out in May, according to an AP count.
An ongoing massive Iraqi-led offensive dubbed Operation Lightning is aimed at curbing the constant violence. According to Iraqi government figures obtained Wednesday, 670 Iraqis were killed in May, a 38 percent increase from April, when 485 died. The Iraqi figures do not include U.S. troops.
Some 297 insurgents also were killed in May, an almost 400 percent increase from the 60 militants killed in April. U.S. forces killed almost 140 during two May offensives in western Iraq, while many others were suicide bombers.
The government did not provide figures for every year or the months before April.
The suicide bomber exploded his vehicle at the main checkpoint to Baghdad's airport, the U.S. military and police said. The airport is located at the end of a 10-mile-long highway dubbed by many Iraqis the "Street of Death" because it is the frequent target of suicide bombings and ambushes.
The al Qaeda in Iraq terrorist group claimed responsibility in an Internet statement that could not be authenticated.
The blast struck near the Abbas Ibn Firnas statue, commonly known as the "Flying Man," which depicts a winged medieval Arab astronomer. The statue is located between two parking lots.
"Me and some colleagues at Iraqi Airways were waiting in line when we saw a speeding car, then we heard a big explosion," said Ghassan Yassin, who was among the 15 wounded. "The next thing I realized is that my car was on fire. I got out through the window after the doors were jammed due to the explosion."
The military said insurgents then attacked the entry point with small arms fire. No coalition forces were wounded.
The attack near the airport, which scores of foreigners use daily to enter and leave the country, highlights the difficulties faced by U.S. and Iraqi forces in trying to defeat the insurgency and safeguard Iraqi's most vital facilities.
In New York, Iraqi Foreign Minister Hoshyar Zebari said U.S.-led forces must remain in Iraq until the country's own soldiers and police can take responsibility for securing the nation amid its continuing insurgency.
Zebari told the U.N. Security Council on Tuesday that he was "concerned" about U.S.-led forces leaving before Iraqi security forces were ready to protect this country from insurgents.
"I'm a realist, OK, and we've seen that before. We need to complete this mission with their help," Zebari told the AP late Tuesday. "We are getting very close. The riding is getting tougher."
The multinational force has about 138,000 U.S. troops and more than 22,000 soldiers from 27 other countries.
Acting U.S. Ambassador Anne Patterson, speaking on behalf of the multinational force, told the Security Council it will not remain in Iraq any longer than necessary, but "no specific timeline for the withdrawal" has been set.
But if Iraqi authorities want the troops to stay, they should not leave "until the Iraqis can meet the serious security challenges they face," she said.