Official and local sources said that a US drone fired three missiles at a house in Darand Sheikhan area of Lower Orakzai Agency early on Wednesday.
They said the death toll is expected to rise as rescue operation is underway in the area.
On Tuesday, Pakistan condemned the non-UN-sanctioned US assassination drone strikes in the northwestern tribal belt of the country as “unlawful and counterproductive.”
“We are of the firm view that these [strikes] are unlawful, counterproductive and hence unacceptable," Pakistan's Foreign Ministry spokesman Abdul Basit said on Tuesday.
The US regularly carries out attacks by unmanned aircraft on Pakistan's tribal regions, claiming that the airstrikes target militants affiliated with the Taliban and al-Qaeda terrorist groups, but locals say civilians are the main victims.
The aerial attacks, initiated by former US President George W. Bush, have escalated under President Barack Obama.