UPDATE 1-U.S. drone attack kills at least 8 in Pakistan

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PESHAWAR, Pakistan, May 12 (Reuters) - Suspected U.S. drone aircraft fired missiles in a Pakistani region on the Afghan border on Tuesday, killing at least eight people, military and intelligence officials said.

The attack took place in a mountainous region of South Waziristan, a known al Qaeda and Taliban hotbed, the officials said.

"We have at least eight dead in the attack," said a Pakistani military official who declined to be identified.

The target of the attack was not immediately known, he said.

The United States began stepping up drone attacks in Pakistan last year. There has been no let-up since President Barack Obama's administration took office in January, despite complaints from the Pakistani government.

The United States has carried out about 40 drone air strikes since the begining of last year, most since September, killing more than 320 people, according to a tally of reports from Pakistani security officials, district government officials and residents.

There have been 16 attacks this year, with five in April.

At least five militants were killed on Saturday in a drone attack, also in South Waziristan.

Pakistan says the drones violate its sovereignty and undermine efforts to deal with militancy because they inflame public anger and bolster militant support. (Reporting by Alamgir Bitani; Writing by Augustine Anthony; Editing by Robert Birsel and Valerie Lee)