QUETTA, Pakistan (AFP) - Pakistani security forces raided a compound in the country's troubled south-west and killed four militants linked to an attack on a police academy earlier in the week, officials said on Friday (Oct 28).

The raid in Quetta, the capital of strife-riven Balochistan province, was carried out late on Thursday (Oct 27) following an intelligence tip-off about the presence of fighters from the Lashkar-e-Jhangvi (LeJ) militant group.

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

Speaking off the record, a police official said the militants belonged to the LeJ - a faction of which claimed it had worked with the Islamic State in Iraq and Syria (ISIS) group to carry out the Monday (Oct 24) night raid that killed 61 people, the deadliest assault on a security installation in Pakistan's history.

ISIS 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 ISIS 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 home-grown 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 tocarry out major assaults from time to time.

The emergence of ISIS 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".