Qatar announced on Monday it had shot down two Iranian bombers.
The Soviet-era Su-24s are the first known Iranian aircraft brought down over the Gulf since the regional war started two days ago.
The Gulf state's Ministry of Defence said the planes were hit by Qatar's air force. Five Iranian drones and seven ballistic missiles were also intercepted.
"The threat was addressed immediately upon detection, in accordance with the operational plan, as all missiles were shot down before reaching their targets,” the ministry said.
Iran's Islamic Revolutionary Guard Corps said it has launched 12 waves of attacks since the US and Israel launched their offensive on Saturday, killing Iranian supreme leader Ayatollah Ali Khamenei.
The IRGC said the attacks – Operation True Promise 4 – have been launched by its air and naval branches and used "more advanced” missiles than during the 12-day war with Israel last June. But the IRGC, who were holding drills in the days before war started, have not announced any use of bombers to attack the Gulf.
Attacks have reached Saudi Arabia, Qatar, Oman, Kuwait, Jordan, Bahrain and Iraq, while Iranian ally Hezbollah launched rocket fire in Lebanon. The International Institute of Strategic Studies says Iran has dozens of Russian and Soviet warplanes at its disposal including the Sukhoi Su-24, known by the Nato code name Fencer.
The supersonic aircraft, whose first model entered service in 1974, has been sold to Iran, Iraq, Libya and Syria among other countries. Russia and Iran have close military ties. Iran has supplied weapons to Russia's war effort in Ukraine, notably Shahed attack drones.
Moscow, in turn, is reported to have signed a $590 million deal in December to sell Russian-made portable missiles to Iran. Russian President Vladimir Putin on Sunday condemned the killing of Mr Khamenei as a breach of "human morality”.
Qatari officials did not give details of where the Iranian-owned planes were shot down. They earlier said Iranian drones had attacked a power plant and a site belonging to oil and gas company QatarEnergy.
The Defence Ministry said damage was being assessed. A water tank was attacked at the power plant in Mesaieed, while the second drone "targeted an energy facility” in Ras Laffan Industrial City.
No casualties were reported, but Qatar's production of liquefied natural gas was halted. QatarEnergy is the biggest producer of LNG in the world, accounting for 20 per cent of global supply.
Three US fighter jets earlier came down over Kuwait in what appeared to be a case of friendly fire. Kuwaiti air defences shot down the F-15E Strike Eagle fighter jets.
