At least 16 people were killed in four consecutive U.S. drone strikes Tuesday afternoon in Pakistan's northwest tribal area of North Waziristan, reported local media.

In the first strike, the U.S. drones fired two missiles at two houses in Tehsil Ghulam Khan area of North Waziristan, killing five people inside the houses.

In the second strike which came minutes after the first one, three people were killed while a local Urdu TV channel DAWN claimed 12 people died in the missile attack.

In the third strike, four people were killed and two others injured.

The second and third strike were launched in the same area as the first one, but local media gave no more details such as the targets of the attack.

The fourth strike left four people dead when two missiles were reportedly fired at a vehicle in the Datta Khel area of North Waziristan.

North Waziristan, which borders Afghanistan, is believed to be a safe heaven of insurgents and militants. A total of 113 people have been killed in 15 drone strikes in northwest Pakistan so far this month.