Stores and schools were closed in several other predominantly Shiite neighborhoods in the capital, apparently in compliance with the civil disobedience order. Armed Mahdi Army members were seen patrolling the streets in some Shiite neighborhoods of the capital.
In Basra, Iraqi soldiers and police battled Mahdi fighters for control of key neighborhoods in Iraq's second-largest city, 340 miles southeast of Baghdad. The fighting erupted a day after al-Maliki flew there to supervise a security crackdown against the militias.
Police and hospital officials reported that at least 22 people had been killed and 58 wounded in the clashes. Iraqi authorities on Monday imposed an indefinite nighttime curfew on the city.
AP Television News video showed smoke from explosions rising over the city and Iraqi soldiers exchanging gunfire with militia members.
Basra accounts for most of Iraq's oil exports, but an oil ministry official, declining to be identified because he wasn't supposed to publicly discuss the sensitive issue, said production and exports had not been affected by the fighting.
Curfews were also imposed in the Shiite cities of Kut and Nasiriyah.
In Baghdad, suspected Mahdi Army gunmen exchanged gunfire Tuesday with security guards of the rival Shiite Supreme Islamic Iraqi Council in Sadr City, police said.
The rising tension led many people in Shiite neighborhoods to stay at home rather than venture into contested streets.
Athra Ali, 27, a government employee who lives in the Hurriyah neighborhood, said she decided not to go to work after seeing many shops closed and streets abandoned.
A university lecturer at Baghdad's Mustansiriyah University also said the institution had closed early and sent students home.
In Basra, Col. Karim al-Zaidi, spokesman for the Iraq military, said security forces were encountering stiff resistance from Mahdi Army gunmen.
The US military said Tuesday that five suspected militants were killed in Basra while attempting to place a roadside bomb. Ten others were injured after being spotted conducting suspicious activity, the statement said.