Pakistan's interior minister on Wednesday announced a breakthrough in the case of last week's Karachi bus attack that killed 47 minority Shiite Muslims, saying police have arrested the suspected mastermind and several gunmen involved in the assault, Fox News reported.

Chaudhry Nisar Ali Khan's announcement in Islamabad came just hours after the army said it had killed 13 militants in airstrikes in a tribal region bordering Afghanistan.

Khan said the arrests were the result of an "excellent coordination between police and intelligence agencies" in Sindh province, of which Karachi is the capital.

The minister did not say when the arrests were made or give any details on the affiliation of the gunmen. He said some of those arrested confessed to taking part in the attack.

Both a Pakistani militant group linked to Daesh, which is fighting in Iraq and Syria, and a Pakistani Taliban splinter group have claimed responsibility for the May 13 assault during which gunmen stormed a bus with members of the Ismaili Shiite branch, forced them to bow their heads, then shot and killed them.

Earlier Wednesday, the military said its jets killed 13 militants in latest airstrikes near the Datta Khel village in North Waziristan, where the army has been carrying out a major operation against local and foreign militants since last June.

There were no further details on the identity of the suspected militants. Pakistani tribal areas are off limits to journalists.