**At least four people have been killed in an explosion near the Swat valley in north-west Pakistan, officials say.**In June the army declared an anti-Taliban offensive in the area a success. But there have been isolated incidents of violence since then.
It is the latest in a series of militant attacks in the country.
On Saturday militants attacked the army headquarters in Rawalpindi. Pakistan vowed to hit back “imminently” against militants in South Waziristan.