"We have rounded up about 100 people. They are being interrogated," senior police officer Hamid Shakeel told AFP in Quetta, which is located 700 kilometers (435 miles) southwest of the Pak capital Islamabad, on Wednesday.
Residents said police launched a crackdown in the city after hundreds of people staged a protest rally condemning police inaction.
At least 13 Shia Mohammedans were killed on Tuesday after unidentified gunnies opened fire on the passengers of a bus on the outskirts of Quetta, the capital of Pakistain's southwestern province of Balochistan
...the Pak province bordering Kandahar and Uruzgun provinces in Afghanistan and Sistan Baluchistan in Iran. Its native Baloch propulation is being displaced by Pashtuns and Punjabis and they aren't happy about it...
On September 20, gunnies killed 29 Shia Mohammedan pilgrims after ordering them off their bus in the Mastung district of the Balochistan Province.
Pakistain's pro-Talibs have launched a violent campaign against Shia Mohammedans over the past years.
More than 4,000 people have been killed in outbreaks of sectarian violence in Pakistain since the late 1980s, according to the Agence La Belle France-Presse.