More than 50 people have been killed and 200 injured in a suicide attack targeting a Shia Muslim rally in Pakistan's southwest city Quetta.

Police officers said the bomber was among the 450-strong crowd and had detonated the device on reaching the main square in the city on Friday.

The explosion triggering chaotic scenes, with some people set on fire as others fled or lay on the ground to avoid ongoing gunfire.

The bomb appeared to target the rally being held for al-Quds day, an international event held every year by the Shia community in opposition to Israel's control of Jerusalem and to show solidarity with Palestinian Muslims.

It is the second time this week the Shia minority has been targeted with a deadly attack.

Al Jazeera's Tarek Bazely reports.