Iraq's Shi'ite prime minister has called for calm as a one-day ban on automobile traffic in Baghdad imposed an eery quiet on the city.

Prime Minister Ibrahim al-Jaafari appealed to the nation's clerics Friday to avoid inflammatory language during Muslim prayers.

On Thursday night, gunmen killed at least 18 Shi'ite workers in attacks on two factories in a small town near Baghdad. 

As the traffic ban went into effect Friday, Iraqi police and troops patrolled streets in the capital.  The ban is a new effort to curb sectarian violence that has killed hundreds since the bombing of a Shi'ite shrine last week.

Meanwhile, a coalition of Sunni and Kurdish politicians has called on Iraq's Shi'ite prime minister to step down.

The politicians say Ibrahim al-Jaafari is an obstacle to political unity, but a spokesman for the Shi'ite bloc says it continues to back him for another term as prime minister. 

The political jockeying comes as some Sunni leaders blame the Shi'ite-led government for failing to stop continuing violence in the war-torn country.

Iraq's political factions have been meeting to try and form a unity government.

Some information for this report was provided by AFP and Reuters.