Security forces raided a compound in Quetta and killed four militants linked to an attack on a police academy earlier in the week, officials said Friday.

The raid in Quetta, the capital of strife-riven Balochistan province, was carried out late Thursday following an intelligence tip-off about the presence of fighters from the Lashkar-i-Jhangvi (LJ) militant group.

“A team of anti-terrorist force (ATF) raided the compound and killed four militants after an exchange of gunfire,” a senior local police official Abdullah Afridi told AFP.

Speaking off the record, a police official said the militants belonged to the LJ — a faction of which claimed it had worked with the militant Islamic State group to carry out the Monday night raid that killed 61 people, the deadliest assault on a security installation in Pakistan's history.

IS had previously also claimed the raid and released photos of the fighters involved, one of whom bore a strong resemblance to an attacker who was killed by security forces in the assault.

The extent of any material support to local groups from IS remains unclear, but affiliation with the notoriously brutal outfit brings the promise of a far higher profile.

The Balochistan government has also formed a joint investigation team (JIT) comprising officials from the army, police and intelligence agencies to probe Monday's attack.

Pakistan has been battling a homegrown Islamist insurgency since shortly after the US-led invasion of Afghanistan in 2001, though overall levels of violence have dropped following a series of military offensives in the country's western tribal regions.

Monday night's raid though served as a grim reminder that militant groups are still able to carry out major assaults from time to time.

The emergence of IS in Pakistan is seen as a major blow to the country's long-running efforts to quell the insurgency, and comes as the group's key rival Al Qaeda is losing strength in what was once its “home ground”.