A suspected U.S. drone strike killed 12 alleged militants in Pakistan's tribal region on Wednesday morning, intelligence officials told CNN.

It was the latest in a series of aerial assaults targeted at insurgents in North Waziristan, one of seven districts in Pakistan's volatile tribal region bordering Afghanistan.

In Wednesday's incident, seven missiles were fired on a suspected hideout of suspected militants in the Darga Mandi area, said two intelligence officials.

The officials asked not to be named because they were not authorized to speak to the media.

The United States does not comment on suspected drone strikes. But it is the only country in the region known to have the ability to launch missiles from drones - which are controlled remotely.

Security analysts have described North Waziristan as a haven for various factions of Afghan and Pakistani Taliban and al Qaeda militants.

The majority of reported strikes this year have hit targets in the district, analysts said.

On Tuesday, two strikes killed 13 alleged militants. On Sunday, another five died. And last week, 29 suspected militants in the region were killed.

In June, the U.N.'s senior official for extrajudicial executions, Philip Alston, said the United States should explain the legal rationale for the CIA's campaign of drone strikes in northwest Pakistan, which he characterized as "a vaguely defined license to kill" that has created "a major accountability vacuum."

Alston also urged the Obama administration to disclose the number of civilians killed in the drone strikes.

The civilian death toll has angered Pakistanis, less than a tenth of whom support the strikes, said Peter Bergen, CNN's national security analyst.

According to the New America Foundation, a Washington-based think tank where Bergen is a fellow, the drones program in Pakistan has reportedly killed more than 1,000 people since 2004. Many of the casualties were civilians, the foundation said.

– Journalist Nasir Dawar contributed to this report.