Gunmen have killed at least 25 people in Karachi in the past 24 hours, raising tensions in Pakistan's largest city as voters cast ballots Sunday to replace a provincial lawmaker murdered in August.
Police said they were still investigating the motives behind the shootings, but many so-called "target killings" in Karachi have been linked to gangs controlled by the city's main political parties, which have been feuding for much of the last 20 years.
"We cannot say whether all the killings were politically motivated or some gangs were involved because the killings took place in different parts of the city and were not confined to the area where the elections were being held," Karachi police Chief Fayyza Leghari said.
The two parties most linked to violence in Karachi _ the Muttahida Quami Movement and the Awami National Party_ have their electoral bases in different ethnic groups that make up a large chunk of the city's population.
The MQM claims to represent the Urdu-speaking descendants of those people who came to Karachi from India soon after the birth of Pakistan in 1947. It is secular and likes to speak out against the so-called Talibanization of the city, a jab at the Awami National Party, which represents the ethnic Pashtuns from the Taliban heartland in the northwest.
Raza Haider, the member of the provincial assembly who was gunned down in August, was a senior member of the MQM. In the wake of the shooting, the MQM accused the ANP of supporting Islamist militants suspected of being behind the murder _ an allegation denied by the ANP.
Both parties were competing for Haider's vacant seat, but the ANP announced Saturday evening that it would boycott the election, saying the MQM would rig the vote. The shootings began around the time the ANP made its announcement.
At least 25 people have been gunned down in Karachi since Saturday evening, said Zulfiqar Mirza, the home minister of Sindh province, where Karachi is the capital. He called on party leaders to come forward to "help us turn Karachi back into the city of light and peace."
"If someone has a complaint, it should not be settled on the street," Mirza told a news conference. "It is disappointing that we are shedding our priceless blood with our own hands."
The dead include members of a broad range of ethnic groups in the city, he said.
Haider Abbas Rizvi, a senior MQM leader and member of Parliament, accused the ANP of being behind the shootings, saying "19 of our workers and supporters have been killed so far."
Senior ANP member Amin Khattak denied the accusation, saying, "we are not involved in killings, and I think that this blame game should be stopped."
Leghari, the police chief, said at least three of the killings did not seem to be politically motivated and were carried out during "other criminal offenses."
The killings were reminiscent of the violence that followed Haider's murder. At least 45 people died in the days following his killing.
Police have arrested at least 60 people in connection with the most recent shootings, Mirza said. But few killers in such cases have ever been brought to justice, and motives for the attacks have not been revealed.
The rising tension between the MQM and the ANP represents a serious danger to stability in Karachi, a city of some 16 million people and Pakistan's commercial hub.
Pashtuns have been arriving in the city in greater numbers in recent years, fleeing Pakistan army offensives against the Taliban. An estimated 4 million Pashtuns are now in Karachi and many live in sprawling slums on the outskirts that are "no-go" areas for authorities.
Violence has surged in Karachi this year with hundreds of people slain in target killings. This increase has echoes of the city's bloody past.
In the 1980s and 1990s, Karachi was regularly convulsed by violence in which hundreds were killed. MQM leader Altaf Husein fled to London in 1992 as a result of that bloodshed and was granted asylum. He regularly addresses large gatherings of supporters by telephone link.