Islamabad, Pakistan (CNN) -- A suspected U.S. drone strike in Pakistan's tribal region killed four suspected militants Monday, Pakistani intelligence officials told CNN.
Two intelligence officials said the suspected drone fired two missiles at a vehicle carrying militants in the Mir Ali area of North Waziristan, one of the seven districts of Pakistan's volatile tribal region bordering Afghanistan.
The intelligence officials asked not to be named because they were not authorized to speak to the media.
Based on a count by the CNN Islamabad bureau, Monday's suspected drone strike was the 27th this year compared with 111 in all of 2010.
It was the latest in a spate of suspected drone attacks that the United States has carried out in Pakistan since U.S. forces killed al Qaeda leader Osama bin Laden in the early morning hours of May 2.
The recent increase, however, probably is not due to intelligence gained from bin Laden's compound, Bill Roggio, a military affairs analyst and editor of the Long War Journal, has said.
"What has happened since the bin Laden raid is that the U.S. has not felt pressured to dial back the attacks due to Pakistani sensibilities," he said.
On Sunday protesters in Pakistan held a sit-in near the country's main port in Karachi, demanding an end to U.S. drone strikes.
The United States does not officially acknowledge drone attacks in Pakistan, but it is the only country operating in the region with the capacity to carry out such strikes. It was once widely believed that the program had the tacit approval and cooperation of Pakistan's intelligence agency.
CNN's Nasir Habib contributed to this report.