Tehran says it targeted a American-linked air base in the region after Washington hit sites in southern Iran following a drone incident The Iranian Islamic Revolution Guards Corps (IRGC) has said it carried out a retaliatory strike on an air base used by the US after American forces attacked targets in southern Iran over the weekend.The latest exchange has further strained a fragile ceasefire reached in April after more than a month of fighting triggered by US and Israeli attacks on Iran. Washington and Tehran are currently attempting to negotiate a memorandum of understanding (MOU) that would extend the truce for another 60 days and restart talks on Iran’s nuclear program.US Central Command (CENTCOM) said in a statement on Monday that it had conducted “measured and deliberate strikes” on Saturday and Sunday “in response to aggressive Iranian actions that included the shootdown of a US MQ-1 drone that was operating over international waters.” It accused Tehran of “unwarranted… aggression during the ongoing ceasefire.”Iran announced the downing of the UAV on Sunday, saying it was hit due to violations of the country’s airspace over the Persian Gulf. Read more US military secretly guiding ships through Strait of Hormuz – NYT According to CENTCOM, the “self-defense strikes” by US fighter jets targeted Iranian radar and command and control sites for drones in Goruk and Qeshm Island.Later in the day, the IRGC said it had responded to what it described as an American strike on a communications tower on the Islamic Republic’s Sirik Island.The Iranian military “targeted the air base, from which the [US] attack originated, and the predetermined targets were destroyed,” it said in a statement.The statement did not identify the location of the targeted base, although Kuwait’s KUNA news agency earlier reported that the Gulf nation’s air defenses had intercepted incoming missiles and drones.The IRGC warned “that if the aggression is repeated, the response will be completely different” and that the US would be to blame.Tehran has been making changes to a draft MOU after reports of US President Donald Trump sending a tougher proposal to Iran on Sunday, Tasnim news agency reported. The exchanges on the text of an MOU “are ongoing, with both parties regularly proposing amendments,” the agency’s source said. READ MORE: Trump pushes for last-minute changes to Iran peace draft – media Top Iranian negotiator Mohammad Bagher Ghalibaf previously stressed that Tehran has no trust in promises made by the US and “will not approve any agreement until we are sure that we have upheld the rights of the Iranian nation.”