Many shops and businesses in the Pakistani city of Karachi are closed amid fears of fresh unrest after five days of suspected sectarian violence.
The hardline Islamist alliance, the MMA, called the one-day strike in protest at what it said was government failure to prevent the violence.
Nearly 30 people have died in a number of attacks across the country blamed on rivalry between Sunni and Shia Muslims.
In the latest violence, about 100 Sunni Muslims rioted in eastern Karachi.
Shops burned
Karachi's financial markets remained open and much of the transport was still operating but many businesses and shopping centres closed their shutters.
Merajul Huda, Karachi head of one of the MMA parties, the Jamaat-e-Islami, told Associated Press: "The public has given full support to the strike against terrorism. Business in the city is closed."
One shopkeeper, Tahir Sultan, said he supported the strike as a "denouncement of terrorism and to mourn innocent victims".
Another, Faheem Ahmed, said: "It's better to close than face any damage or loss."
Police said the southern port city was mainly tense but calm.
Shia leaders had declared three days of mourning over the violence and had urged their followers to remain peaceful.
However, about 100 Sunnis were reported to have burned shops and thrown stones in the eastern Malir district in protest at the death of a man allegedly killed in a shoot-out with Shias on Tuesday.
The unrest started on Friday when a suicide bomber in Islamabad killed 19 people and wounded nearly 100 in an attack on a shrine where hundreds of Shias had gathered.
On Monday in Karachi, five people were killed and about 20 others wounded in a suicide attack on a Shia mosque.
Later the same day, six people were killed when a mob set a Kentucky Fried Chicken outlet ablaze in the city.
Also on Monday in Karachi, leading local MMA politician, Aslam Mujahid, was kidnapped and shot dead, although the motive was unclear.
Qazi Hussain Ahmed, head of the Jamaat-e-Islami, said the violence was not sectarian but "terrorist activities carried out at the behest of the United States".
Police have arrested 56 people for arson and violent attacks in the city over the past two days.
There have been numerous acts of sectarian and criminal violence in Karachi in recent years.