Iran’s Islamic Revolutionary Guard Corps (IRGC) claimed Tuesday that it shot down a U.S. MQ-9 drone and claimed that an RQ-4 drone and an F-35 fighter jet also entered Iranian airspace before retreating.

The aircraft entered Iranian airspace over the Gulf region, the IRGC said in a statement carried by Iran’s state-run IRNA news agency.

The U.S. aircraft “entered Iranian airspace in the Persian Gulf region and air defense units of the Islamic Revolutionary Guard Corps … identified and shot down an MQ-9 drone,” the statement said.

The IRGC “also fired upon an RQ-4 drone and an intruding F-35 fighter jet,” the statement added, without specifying when the incidents took place.

The force also said it reserves the right “to respond to any ceasefire violation by the aggressor U.S. army.”

Earlier Tuesday, Iran’s semi-official Fars News Agency reported that U.S. and Israeli aircraft struck Iranian vessels south of Larak Island near the Strait of Hormuz, killing “several Iranian nationals.”

The claims could not be independently verified.

The developments come amid Pakistan-led mediation efforts aimed at ending the conflict that began with U.S. and Israeli strikes on Iran on Feb. 28 and was followed by Iranian retaliation.

A cease-fire took effect on April 8 and was later extended indefinitely by U.S. President Donald Trump.