Fresh political violence in Pakistan's southern port city of Karachi has killed 14 people, following inflammatory remarks by a senior member of the country's ruling political party.

Police said Thursday the violence overnight in Karachi erupted after Zulfiqar Mirza, the head of the ruling Pakistan People's Party in Sindh province, criticized the rival Muttahida Quami Movement party, which pulled out of the ruling coalition last month. Mirzi called MQM's leaders criminals and also criticized the city's Urdu-speaking community, which make up MQM's base.

Soon after the comments aired on local television, gunfire broke out and angry mobs set fire to a number of vehicles.

Authorities said they arrested about 160 people following the fighting. Security forces blocked off some streets, and the stock exchange closed early on Thursday after very light trading.

Mirza later issued a statement apologizing for his comments, saying they were personal opinion and not that of the party.

A surge in political and ethnic violence in Karachi has killed at least 100 people since last week. Additional police and paramilitary personnel have been deployed to try and quell the latest surge in political violence.

Last week's violence involved the MQM and supporters of the Awami National Party, which largely represents ethnic Pashtuns.

Some 18 million people live in Pakistan's economic hub of Karachi. The city has also been the scene of sectarian violence between Sunni and Shi'ite Muslims and militant attacks.

The Human Rights Commission of Pakistan says 490 people died in targeted killings in Karachi in the first half of this year.

Meanwhile, officials in the southwestern town of Chaman, along the Afghan border, said a blast ripped through a house used by Afghan refugees, killing four people and wounding 10 others. At least two of the dead were children. Authorities say the house was being used to store explosives and weapons.