They say two missiles hit the Shawal area of North Waziristan when the men were crossing on foot into Pakistani territory from Afghanistan.
The two officials spoke on condition of anonymity because they were not authorised to brief reporters.
They said the men have not been identified.
North Waziristan is home to a mix of Pakistani, Afghan and al-Qaeda-linked foreign militants.
The US drone programme is a source of extreme tension between the two countries.
Washington says it needs to send drones after dangerous militants because the Pakistani government refuses to engage them militarily.