(CNN) -- Four suspected U.S. drone strikes have pounded Pakistan's tribal region since the American military killed terror leader Osama bin Laden, actions that signal an uptick in the U.S. fight against Islamic militants.
The latest was Friday, when four suspected militants died in the Datta Khel region of North Waziristan, according to two Pakistani intelligence officials, who said an unmanned aircraft fired four missiles at a militant's vehicle.
Drone strikes have been controversial in Pakistan because of concerns over civilian deaths and disrespect for Pakistan's sovereignty.
"I don't think the U.S. cares about the Pakistani sensibilities," said Bill Roggio, a military-affairs analyst. "I think it's game back on."
North Waziristan is one of the seven districts of Pakistan's volatile tribal region bordering Afghanistan, and Datta Khel has a strong presence of militants, Roggio said.
Based on a count by the CNN Islamabad bureau, Friday's suspected drone strike was the 24th so far this year compared to 111 in all of 2010.
The Long War Journal, a website that provides analyses and reporting on war-related matters, said the U.S. military launched only two strikes in April and seven in March, in both North Waziristan and South Waziristan.
Roggio, the managing editor of The Long War Journal, told CNN that there have been drone-strike pauses during spring months in the past, but he said the latest lull came during problems between the United States and Pakistan.
He cited the disagreements over the case of Raymond Davis, the CIA contractor who had been incarcerated and later released after allegedly shooting and killing two Pakistanis, and Pakistani rage about a couple of the drone strikes.
But Roggio said he believes the dynamics have changed after bin Laden was killed May 2 in a hideout in the Pakistani military garrison town of Abbottabad.
He said there's a lot of U.S. impatience with the Pakistanis and that's "no big secret after the bin Laden raid."
He emphasized that the Pakistani military hasn't taken on militants in the Datta Khel region, which Roggio calls a "snake pit" and a "known al Qaeda hub."
"It's clear now they are just gonna keep doing it," he said, referring to the drone strikes.
The other drone strikes since bin Laden's death occurred last Friday, Tuesday, and Thursday.
North Waziristan is in the same dangerous northwestern Pakistani swath as the district of Charsadda in Khyber Pakhtunkhwa province, where a twin suicide bombing killed at least 80 people on Friday.
The province borders Mohmand Agency, one of the seven district tribal regions where the Pakistani Taliban members are based.
The Pakistani Taliban said it carried out the bombing in retaliation for the killing of terror leader Osama bin Laden.
Nearly all of those slain were military recruits who had just completed their training, a government official said. About 140 others were injured.
Mohmand is believed to be a hideout for Taliban fighters and al Qaeda-linked militants fleeing last year's military operation in the district of South Waziristan and ongoing U.S. drone strikes in North Waziristan.
The Pakistani army has carried out numerous ground and air operations in Mohmand but they haven't been able to stamp out the militants.
Last December, around 150 militants ambushed six security checkpoints in Mohmand, killing 11 Pakistani soldiers, officials told CNN.
Earlier in December, a twin suicide attack targeting a government building in Mohmand killed at least 40 people.
Roggio said the Pakistani Taliban represents a confederation of Taliban groups in northwestern Pakistan, where they are based.
They make attacks on Pakistani targets and cross the border into Afghanistan for attacks, Roggio said.
They are different from the Afghan Taliban, focused on re-establishing the Islamic Emirate in Afghanistan. The group is headquartered in Quetta, Pakistan.
Both groups swear allegiance to Taliban leader, Mullah Omar, and have close links to al Qaeda, Roggio said.
Journalist Nasir Dawar and CNN's Nasir Habib contributed to this report.