KARACHI Six people were wounded when unidentified attackers hurled a grenade at a Karachi mosque during evening prayers on Wednesday, police said.
The attack, on top of the violent deaths of more than 12 people on Tuesday night, deepened fears of instability in Pakistan's commercial hub.
Police and officials said a total of 70 people had been killed since Monday, following the assassination of Raza Haider, a lawmaker in the Muttahida Quami Movement (MQM), the dominant political party in the city.
The government blamed Taliban insurgents and the banned militant group Sipah-e-Sahaba Pakistan (SSP) for his killing.
Some analysts said persistent violence could damage the already struggling economy. Karachi is home to the country's main port, the central bank and the stock exchange, and home to some 18 million people.
Analysts' concern was heightened by the flight of Taliban militants to Karachi, a teeming city that is easy to hide in, after army offensives against their strongholds in the northwest.
"Four people were shot dead in one incident late last night, while six to seven trucks parked under a bridge were also burned," Karachi police chief Waseem Ahmed told Reuters.
No further information was immediately available about the grenade attack on the mosque.
Hospital sources and officials said at least 12 people were shot and killed and more than 150 wounded overnight in an escalation of the violence that has gripped the city since Haider and his bodyguard were shot down at a funeral.
The MQM has called for three days of mourning.
Early on Wednesday, unknown people set fire to several mobile phone shops in a main market in the city.
Police said more than 50 vehicles have been burned and dozens of shops set on fire since Haider's killing. Dozens of people have been arrested on charges of violence, they said, and most shops and fuel stations in the city stayed closed on Wednesday.
"The situation is not good. I will wait for a few hours to see how it goes and if other people in the market also open shops, then I will as well," said Muhammad Jawaid, standing outside his closed bakery.
Trading was again dull at the Karachi Stock Exchange.
Karachi has a long history of ethnic, religious and sectarian violence. It was a main target of al Qaeda-linked militants after the September 11, 2001, attacks on the United States, when Pakistan joined the U.S.-led campaign against militancy, and foreigners were attacked in the city several times.
Including this week's killings, officials say at least 214 people have been killed in targeted attacks since the start of the year, though analysts and political parties say the number is likely much higher.
(Additional reporting by Sahar Ahmed; Editing by Michael Georgy and Miral Fahmy)