BAGHDAD, Iraq – Iraqi authorities pulled a brigade of about 700 policemen out of service Wednesday in its biggest move ever to uproot troops linked to death squads, aiming to signal the government’s seriousness in cleansing Baghdad of sectarian violence. The government move came amid steadily mounting violence, particularly in the capital. A U.S. military spokesman said the past week had seen the highest number of car bombs and roadside bombs in Baghdad this year.

Four U.S. soldiers patrolling in Baghdad were killed by gunmen on Wednesday, the U.S. military said, also announcing the deaths of two other soldiers a day earlier in Baghdad and the northern city of Kirkuk. The deaths brought to 21 the number of Americans killed in combat since Saturday.

The suspension of the police brigade was the first time the Iraqi government has taken such dramatic action to discipline security forces over possible links to militiamen, though some individual soldiers have been investigated in the past. Baghdad’s Sunnis fear the Shiite-led police, saying they are infiltrated by militia death squads who snatch Sunnis and kill them.