ISLAMABAD: Uzbek fighters were involved in the all-night siege of Karachi airport that killed 37, insurgent sources said Wednesday, highlighting how the Pakistani Taleban (TTP) can draw on international militant networks to carry out major attacks.

The Islamic Movement of Uzbekistan (IMU), an Al-Qaeda affiliate that has been mainly based in Pakistan’s tribal belt since the US-led invasion of Afghanistan in 2001, claimed the “martyrdom” of 10 of their fighters during this week’s assault in a statement posted on various Taleban-linked websites.

The attack extinguished a nascent peace process and raised questions about how the Taleban were able to penetrate the airport serving Pakistan’s economic hub.

A senior Pakistani Taleban official confirmed that Uzbek fighters were involved in the attack but did not say how many.

He told AFP: “The attack on the Karachi airport was a joint operation of TTP and Islamic Movement of Uzbekistan.

A senior security official indicated that the group was partly Uzbek and partly Pashtun, while a second intelligence official in Karachi said the attack may have been coordinated with the help of Lashkar-e-Jhangvi, the sectarian militant outfit deeply embedded in Pakistan’s major cities.

“We believe that the LeJ has coordinated the attacks,” the Karachi official said.

Karachi police meanwhile announced Wednesday they would press murder and terrorism charges against Taleban spokesman Shahidullah Shahid, 10 “unknown” attackers and accomplices, in what was seen as a symbolic move.

Ten heavily armed militants laid siege to Karachi airport throughout Sunday night and the early hours of Monday morning in one of the most brazen attacks on a key installation in recent years.

Security analyst Imtiaz Gul said IMU fighters had migrated to Pakistan’s tribal areas after being forced to flee from Afghanistan following the US-led invasion.

“They have been under the protection of the Pakistani Taleban for some time. The Uzbeks are dependent on them for shelter and survival and are used as their foot soldiers in operations,” he said.

Foreign militants, mostly Uzbeks and Chechens are believed to have been involved in other major attacks in recent years, including on a Karachi naval base in 2011 and the military headquarters in 2009.