The Pentagon said on Monday there was no evidence of any civilian casualties from airstrikes targeting Islamist terrorists in Syria, The Hill reported.

The clarification came after human rights groups claimed that civilians were killed in airstrikes in Syria’s Idlib province last week.

In addition, the groups said the airstrikes were also costly to civilians’ pockets, as they have nearly tripled the price of diesel in Syria's northern Aleppo province.

"We right now don't have anything to corroborate those reports from Syrian activists," said Pentagon spokesman Army Col. Steve Warren, according to The Hill. "We take the matter of civilian casualties very seriously."

Warren added that evidence of civilian casualties from U.S. airstrikes would often be "inconclusive" because the strikes are assessed remotely using surveillance drones.

"The evidence is going to be inclusive often. Remember we're using [intelligence, surveillance and reconnaissance] to determine the battle damage assessment," Warren said.

The U.S. recently began launching airstrikes on targets belonging to the Islamic State (IS or ISIS) in Syria.

These airstrikes have also hit targets belonging to the Al-Qaeda affiliated Al-Nusra Front, a Syrian rebel group, prompting its leader to warn against retaliatory attacks against Western countries.