Gunmen opened fire on Saturday on a van in the city of Quetta, in south-west Pakistan, killing 11 Shia Muslims. Three other people were wounded.
Police suspect it was a sectarian attack. The gunmen escaped.
Afterwards, people from the Shia community burnt cars and offices in Quetta, which is the capital of Balochistan.
Police stepped up their patrols in the area.
Earlier, gunmen killed seven Shia pilgrims at a bus stop in the city centre on Friday.
The BBC reports the Lashkar-e-Jhangvi group said it was behind Saturday's attack.
Its leader Malik Ishaq was recently released after a decade in prison. When asked what he now intended to do, he said the organisation would continue its ''good work'' - fighting those who opposed their version of Islam.
