LAHORE, Pakistan — The Pakistani police on Friday detained the leader of a banned Sunni extremist group that had claimed responsibility for two sectarian bombings that killed nearly 200 people in the past six weeks.

The detention of the leader, Malik Ishaq, who was jailed on separate accusations of hate speech, represented the government’s most prominent step yet against extremists responsible for escalating violence against minority Shiites. But analysts said the detention was unlikely to put Mr. Ishaq’s group, Lashkar-e-Jhangvi — which has led the bloodshed — out of business.

The two devastating bomb attacks that Lashkar claimed responsibility for were targeted against minority Hazara Shiites in the western city of Quetta on Jan. 10 and Feb. 16.

The government’s failure to stem the bloodshed was highlighted by the freedom of movement enjoyed by Mr. Ishaq, who has roamed the country freely since being released from jail in July 2011, reportedly stirring hatred against Shiites.