By Aamir Latif

KARACHI, Pakistan 

At least nine suspected militants have been killed in a U.S. drone strike -- the second in a week -- in Pakistan's restive North Waziristan tribal region on Saturday, officials said. 

A senior military official wishing not to be named told Anadolu Agency that an unmanned predator fired two missiles on a compound in the valley of Shawal near the Afghan border, killing nine suspected militants. 

Five militants were killed in a drone attack on June 1 in the valley, a bastion of militants who have fled from main districts of North Waziristan due to an ongoing military operation against them.

More than 3,450 people have been killed in over 400 drone strikes in Pakistan since 2004. According to international think tanks and human rights groups, including Amnesty international and the Bureau of Investigative Journalism, 70 percent of drone victims were unarmed civilians. 

Despite Islamabad's public objections to U.S. drone strikes, it is rumored to have given tacit approval to the ongoing controversial operations. Pakistan has also developed its own drone to use in the militant-hit northwestern tribal belt.