Pakistan's military says it has killed at least 35 Islamist militants in a northwestern valley increasingly overrun with insurgents.

The army said in a statement Tuesday that the militants died in an overnight operation in Khawaza Khela town in the Swat valley.

It says security forces used helicopter gunships and artillery in the attack.

Swat was once a popular tourist destination, but about two years ago militants began a violent campaign to enforce Taliban-style Islam there.

The state responded with force, but residents say militants increasingly hold sway.