* Air drills covering eastern half of Iran take place amid heightened U.S.-Iran tensions
* Last week Pentagon said Iranian warplanes fired on U.S. drone over Gulf
DUBAI, Nov 12 (Reuters) - Iran launched large-scale air defence drills in the country's eastern half on Monday, Iranian media reported, amid heightened tensions between Tehran and Washington over a military incident last week in the Gulf.
The "Velayat-4" manoeuvres being held this week will span 850,000 square kilometres in Iran's northeast, east, and southeast regions, or about half its total land mass. The manoeuvres will include about 8,000 troops, drawn both from Iran's Islamic Revolutionary Guard Corps (IRGC) and as its regular military, Iranian media reported.
"Various kinds of fixed, mobile, and tactical long-range radars, and fixed, tactical and airborne electronic surveillance systems will participate in this exercise," said Farzad Esmaili, who heads Iran's air defence headquarters, according to state news agency IRNA.
The exercise will also test Iran's bombers, refuelling planes, and unmanned aircraft, Esmaili said.
The Iranian Students' News Agency (ISNA) said on Monday that F-4, F-5, F-7, and F-14 fighter will participate in the exercise.
Missile and artillery systems will also be tested, Shahrokh Shahram, spokesman for the drills, told IRNA on Sunday, and the drills will also focus on improving coordination between Iran's military and the IRGC, a powerful domestic and international actor separate from the regular military.
Last week, the U.S. Pentagon said Iranian warplanes opened fire on an unarmed U.S. drone over international waters on Nov. 1.
Iran said it had repelled an aircraft violating its airspace.
The incident underlined the risk of escalation in tensions between the United States and Iran in an ongoing dispute over Tehran's nuclear programme.
Although the Iranian air drills come just days after the Pentagon's announcement, the exercises appear to have been planned well in advance. In September, Esmaili told ISNA that Iran was planning a large-scale air defence drill in the coming months.
On Sunday, Revolutionary Guards commander Amir Ali Hajizadeh said Iran believed the U.S. drone was gathering intelligence on oil tankers off its shores, according to the Mehr news agency.
Mohammad Ali Jafari, commander of the Guards, said his forces had acted well in repelling the drone.
"Iran's air defence systems and IRGC fighter jets did their job and forced the aircraft out of Iran's skies," Jafari said on Sunday, according to Iran's English-language Press TV. "If such intrusions take place in the future, we will protect our airspace."
Washington, the EU and other bodies have imposed sanctions on Iran's oil trade to press it to halt nuclear research the West fears is aimed at developing the capability to build a nuclear bomb.
The United States and Israel have not ruled out military action against Iran, if diplomacy fails to resolve the row.
Iran denies the charge, saying its nuclear work is purely for peaceful purposes. Iranian officials have threatened to strike U.S. military bases in the region and target Israel if its nuclear sites are attacked.
Iran has carried out a number of military simulations this year, including the "Great Prophet 7" missile exercises in July.
In August, Iran announced that it had tested a short-range missile with a new guidance system capable of striking land and sea targets.