Iraq says it has intensified its inspection of Iranian flights passing through its airspace en route to Syria.

The announcement comes after U.S. Secretary of State John Kerry criticized Iraq for its allegedly lax surveillance of Iranian airplanes.

Ali Mousavi, the spokesman for the Iraqi prime minister, said Iranian flights will be subject to tighter restrictions.

The head of Iraqi aeronautics, Nasser Bandar, said last October that his agency had not inspected any Iranian flights in the past five months because only “suspicious airplanes” are subject to inspection.

Mousavi told the French News Agency that inspections have been ratcheted in the wake of intelligence reports about arms shipments.

He stressed that his agency will tighten its inspection criteria in order to make sure no arms get through to Syria. He added, however, that the intelligence it received has so far not been verified, and no concrete evidence has been provided about any transfer of arms.

While the United States has accused Iran of sending arms to Syria, Iran maintains that it only delivers humanitarian aid to the conflict-torn country.