Pakistani security forces have killed four militants suspected of involvement in a bombing that killed 89 Shi'ites in the southwestern city of Quetta.

Local media say seven other suspects were arrested in a search operation launched Tuesday in Quetta, the capital of Baluchistan province. The alleged mastermind of Saturday's blast was among those arrested.

Officials say some 170 other people were rounded up in Baluchistan.

The Sunni militant group Lashkar-e-Jhangvi claimed responsibility for the attack, which sparked mass protests in such Pakistani cities as Quetta, Karachi and the capital, Islamabad. Protesters demanded justice and a halt to the killing of Shi'ites, a minority in Pakistan.

On Tuesday, Pakistani Shi'ites agreed to end the protests and bury the 89 victims of the attack.

Saturday's attack was the worst in Quetta since a series of bombings on January 10 in a Shi'ite-dominated area of the city killed 92 people. Lashkar-e-Jhangvi also claimed responsibility for those attacks.

The Shi'ite minority in Baluchistan province has been the target of sectarian attacks several times in recent months.

Islamic militants and Lashkar-e-Jhangvi fighters are active in the province, as are Baluch nationalist insurgents fighting to gain a greater share of income from the province's gas and mineral resources.

Sectarian violence claimed more than 400 lives in Pakistan last year.