Suspected US Drone Strike Kills 16 in Northwest Pakistan; Karachi Violence Continues

North Waziristan is known as a base for the Taliban-allied Haqqani group, which is blamed for cross-border attacks against U.S., NATO and Afghan troops in Afghanistan. 

U.S. officials do not publicly comment on the drone strikes, which have raised tensions between Pakistan and the United States in the past. 

Meanwhile, the death toll from four days of violence in Pakistan's southern port city of Karachi has reached at least 26, after at least six more people were killed Tuesday.

The clashes appeared to be between activists from rival political parties - the Muttahida Qaumi Movement and the Awami National Party - which traditionally gather support from different ethnic groups.