BAGHDAD, Aug. 21 — One week after a series of truck bombs hit a poor rural area near the Syrian border, the known casualty toll has soared to more than 500 dead and 1,500 wounded, according to the Iraqi Red Crescent Society, making it the bloodiest coordinated attack since the American-led invasion in 2003.

Dr. Said Hakki, the director of the society, said Tuesday that local Red Crescent workers registering families for aid after the explosions near the town of Sinjar had compiled the new numbers, which dwarf the earlier estimates of at least 250 dead.

The toll, Dr. Hakki said, may yet rise. Emergency workers continued to drag body parts from the site’s dusty rubble. Among the wounded, one in five suffered serious wounds, and hospital officials reported that hundreds of families had taken their broken loved ones home, despite the threat of infection.

“We have declared the villages a disaster area,” said Khidhir Khader Rashu, the mayor of Qahtaniya, one of the villages crushed by the blasts. “What we’ve received of food supplies and other aid so far is not enough, because the scale of destruction is so huge.”