"I was kidnapped, tortured & now forced to leave my #Karachi. Will update," journalist A K Chishti tweeted.
Chishti, a Friday Times reporter, also uploaded his picture showing apparent injury marks on his head.
Chishti writes on counter-terrorism and national security.
Friday Times editor-in-chief Najam Sethi also tweeted, "Ali Chishti, my star Friday Times reporter in Karachi, was yesterday kidnapped and bruised by xxx goons who abused & threatened TFT & me too."
Other journalists have condemned the incident.
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Omar R Quraishi of Express Tribune daily said the Sindh government needs to immediately investigate the abduction and torture of Chishti.
Karachi, Pakistan's largest city and commercial hub, has been plagued by sectarian violence and kidnappings for extortion.
Prime Minister Nawaz Sharif had visited the port city earlier this week and had taken stock of the deteriorating law and order situation.