Story Highlights• NEW: Thousands in Washington protest upcoming fourth anniversary of war's start
• Nineteen bodies found in Baghdad, six in Mosul
• Pentagon on Saturday announces deaths of seven U.S. soldiers
• Three chlorine gas truck bombs explode in Anbar on Friday, U.S. military says
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BAGHDAD, Iraq (CNN) -- Bombers detonated three chlorine-filled trucks in Anbar province, the U.S. military said Saturday.
The attacks killed two police officers and sickened about 350 Iraqis and six coalition force members, the military said.
The bombs went off within three hours Friday afternoon and evening in three different locations: a checkpoint north of Ramadi, Anbar's capital; Amiriya, about 10 miles (16 kilometers) south of Falluja; and the Albu Issa region just south of Falluja. (Watch why chlorine is easy to get in Iraq )
About 250 Iraqis were sickened by chlorine in Albu Issa and 100 in Amiriya. A coalition service member and an Iraqi were injured at the checkpoint near Ramadi, and two police officers were killed in Amiriya.
The bomber who struck near Ramadi used a pickup truck, and the other two bombers were in dump trucks. The Amiriya bomber fled before the explosion; the other two were suicides.
Car bombers have used chlorine as a weapon five times in the past two months in Sunni-dominated Anbar. The province has been a hub for Sunni militants, including those supportive of the group al Qaeda in Iraq.
Soon after two chlorine bomb attacks last month, the military discovered a car bomb factory in Anbar and found a supply of chlorine cylinders there.
At the time, Maj. Gen. William Caldwell, U.S. military spokesman, called the mixing of chemicals and explosives "a change in tactics" and a "crude attempt to raise the terror level."
According to the U.S. Centers for Disease Control and Prevention, exposure to chlorine gas can cause coughing; difficulty in breathing; burning in the nose, throat and eyes; nausea and vomiting.
One of the most commonly manufactured chemicals in the United States, chlorine was employed by the military during World War I as a choking agent, the CDC said.
When chlorine gas is pressurized and cooled, it changes into a liquid; when it's released, it turns back into a gas and spreads rapidly, according to the CDC.
Seven U.S. soldiers die
The Pentagon announced the deaths of seven U.S. soldiers Saturday.
Four died and one was wounded in an explosion in Baghdad. One died Saturday after he was shot during operations in Baquba. (Watch U.S. troops in Kuwait prepare to deploy for the "surge" )
A sixth soldier with Task Force Lightning died Saturday in a non-combat-related incident, which is under investigation.
Another soldier died Wednesday of wounds suffered in a roadside bombing in Samarra on March 5, the military said.
The U.S. death toll in the Iraq war is now 3,211; seven civilian contractors of the Defense Department also have been killed. (Watch a reality check on U.S. troop levels )
About 2,000 Iraqis gathered after Friday prayers in Baghdad's densely populated Shiite stronghold of Sadr City to protest the increase in U.S. troops there, the U.S. military said Saturday.
The protesters rallied at a square near the first joint security station set up in the heart of the Shiite district by the military earlier this month. Similar U.S.-Iraqi stations have been set up across the Iraqi capital as part of the new Baghdad security plan.
The military said the rally was not violent and was organized by radical Shiite cleric Muqtada al-Sadr's organization.
An official with al-Sadr's office told CNN that a Muslim cleric called on those gathered to chant: "No, no, America! No, no, Israel! No, no, devil!"
Al-Sadr's power in Baghdad is concentrated in Sadr City, a Shiite slum of about 2 million people in eastern Baghdad that was named after his father. Al-Sadr's followers include legions of poor, disaffected youths, who also make up the backbone of his Mehdi Army militia. The new Baghdad security plan has been targeting such Shiite armed groups.
CNN's Basim Mahdi contributed to this report.