Story highlights

The bomb is planted outside a store

There has been no claim of responsibility

The attack occurs in Pakistan's restive tribal region

CNN  — 

A blast in Pakistan’s tribal region bordering Afghanistan killed eight and injured at least 21 Thursday, according to a government spokesman.

A roadside bomb detonated in a village market of the volatile Bajaur Agency, said Akbar Khan, a government administrative official. It had been planted outside a store.

Bajaur is one of seven semi-autonomous tribal districts in northwest Pakistan.

There has been no claim of responsibility.

Read more: What’s working in Pakistan

Journalist Aamir Iqbal contributed to this report.