More than 17,000 people ran, walked, biked and rolled across the starting line for the 24th annual Los Angeles Marathon this morning, with cool, overcast weather providing perfect conditions.

The 26.2 mile (42.16km) event began in the heart of downtown LA with the main field sent on their way at 7.24am (PDT).

The course this year followed the 2005 and 2006 route, reported to be the fastest course in the marathon’s history, and passed through some of the city’s most diverse communities before heading back downtown to finish at 5th and Flower.

Participants, volunteers and spectators began arriving before dawn, with many carrying balloons, colorful headgear and American flags to mark the Memorial Day observance.

Competitors in the elite field were competing for a $US100,000 first prize for the first female or male competitor to cross the finish line.

This is the first year the LA race has been run on a Monday in May rather than a Sunday in March, after religious leaders complained of low attendance at religious services due to race-day road closures.

At the same time, US service personnel in Iraq stood-by to compete in a shadow marathon at Camp Taji in Al-Taji, 12.47 miles (20km) north of Baghdad, where the race was scheduled to commence at 10pm local time due to day time temperatures in the region exceeding 100F (37.78C).

The Camp Taji Memorial Day marathon and half-marathon took place on a loop course inside the base, with entry fees being donated to the family members of the 56th Stryker Brigade Fallen Soldiers Fund.

Unlike the LA event, competitors in the Camp Taji event were only competing for bragging rights, along with a medal awarded to competitors.