Pakistan has deployed extra police and paramilitary troops in the southern port city of Karachi in an effort to end a wave of violence that killed at least 36 people this week.

Authorities Wednesday said police had detained some suspects in raids in the city's “troubled” areas. They said many districts remained calm as security forces set up checkpoints in tense areas of Pakistan's commercial hub.

The government also offered a reward to anyone with information leading to the arrest of those carrying out targeted killings.

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 alone.

This week's killings prompted Pakistan's Interior Minister Rehman Malik to warn on Tuesday that the government will take “every possible action to restore peace.”

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

Elsewhere in Pakistan, authorities say gunmen in the southwestern town of Dasht set fire to at least two tankers carrying fuel for NATO forces in neighboring Afghanistan.