A suspected U.S. drone has fired missiles at a vehicle in Pakistan's North Waziristan tribal region, killing four militants.

Local officials said Tuesday's attack took place near Miran Shah, the main town in the tribal area, and that it marked the second missile attack of its kind in two days.

A day earlier, Pakistani security sources said a U.S. drone strike killed four other militants near South Waziristan's main town of Wana. The two largely lawless tribal regions are home to Taliban and al-Qaida-linked militants who also operate across the border in Afghanistan.

Also in South Waziristan, suspected militants Tuesday detonated a roadside bomb near a vehicle carrying Pakistani soldiers, killing two of them. The attack took place as the troops were patrolling near the town of Ladha.

At least 34 people have been killed in a wave of violence in the southern port city of Karachi since Monday. The killings prompted Pakistan's Interior Minister Rehman Malik to warn the government will take “every possible action to restore peace.”

Authorities say 11 people were shot dead in Karachi Tuesday, and that the rest were killed the day before. Karachi has a long history of ethnic, sectarian and political violence by armed gangs suspected of links to Pakistan's main political parties. Officials say the violence killed more than 200 people in the city last month.

Last month, authorities deployed hundreds of extra police and paramilitary troops in Karachi, but the violence has continued.