The Pakistani military has prevented a convoy of thousands of people with the goal of protesting U.S. drone strikes common in the country's tribal areas from reaching South Waziristan.

Authorities stopped the group just short of the tribal region's border Sunday. Pakistani cricket star turned politician Imran Khan had been leading the march, which left Islamabad Saturday.

The protest group had more than doubled to 500 cars by the time it reached Khan's hometown, Mianwali. Local and Western peace activists were traveling alongside supporters of Khan's Movement for Justice party.

Pakistan's government restricts travel to the tribal regions, where it has been battling Taliban and other Islamist militants for years. Ahead of the march, Khan had dismissed concerns that militants would target his group, but a VOA reporter said Khan was riding in an armored vehicle with guards restricting easy access to him.

Drone strikes are a contentious issue between the U.S. and Pakistan. Islamabad says the strikes violate its sovereignty, while Washington believes they are a key tool in the effort to defeat Islamist militants.

Meanwhile, the U.S. embassy in Islamabad says Pakistan has issued a general threat alert for possible terrorist attacks Sunday in Islamabad.

The embassy says in a message on its website that Pakistan's interior ministry warns the attacks could target key government buildings in downtown Islamabad and several major hotels.