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The operation takes place in Kurram Agency

It is part of an ongoing offensive against militants

Islamabad, Pakistan CNN  — 

Security forces killed 20 militants in an operation in northwest Pakistan on Wednesday, military officials said.

Helicopters launched an aerial assault on militant hideouts in central Kurram Agency, a semiautonomous tribal area bordering Afghanistan, the officials said.

The officials did not want to be named because they are not authorized to speak to the media.

A Pakistani soldier died in the operation, the officials said.

The operation was part of an ongoing offensive by security forces against militants in South Waziristan, Kurram and Orakzai agencies.

Journalist Saboor Khattak contributed to this report