LONDON — Some of the world's leading carriers including British Airways, Qantas and Singapore Airlines on Friday suspended flights over the Strait of Hormuz, as Iran-US tensions flare over the downing of a drone.

The suspensions came after the Federal Aviation Administration in the United States issued a Notice to Airmen (NOTAM) "prohibiting US-registered aircraft from operating over the Persian Gulf and Gulf of Oman".

The NOTAM was in response to "heightened military activities and increased political tensions that might place commercial flights at risk", an FAA statement said, as Tehran and Washington engaged in a war of words over Thursday's missile strike on the drone.

The FAA's notice applies only to US-registered airlines, and United Airlines said it was suspending its Newark-Mumbai service in response. But European and Asian operators were taking no chances.

"Our safety and security team are constantly liaising with authorities — including the likes of the FAA — around the world as part of their comprehensive risk assessment into every route we operate," a BA spokeswoman said.

Germany's Lufthansa followed suit in bypassing the Hormuz area.

Dutch carrier KLM said: "Safety is the top priority for KLM.

"The incident with the drone is reason not to fly over the Strait of Hormuz for the time being. This is a precautionary measure."

Regional giants Emirates Airline and Etihad Airways are also re-routing flights away from areas of possible conflict in the Gulf.

"The re-routings have minimally affected the arrival/departure timings of some flights," a spokeswoman for Emirates Airline said on Friday without naming specific countries or provinces that are being avoided. "We are carefully monitoring the ongoing developments and (..) will make further operational changes if the need arises."

Iran's downing of the drone — which Washington insists was above international waters but Iran says was within its airspace — has seen tensions between the two countries spike further after a series of attacks on tanker ships blamed by the US on Tehran.

The Netherlands is still reeling from the downing of Malaysia Airlines flight MH17 in 2014, which was hit a missile over eastern Ukraine's Donetsk region where pro-Russian separatist rebels are battling Ukraine government forces.

All 298 people on board were killed, 196 of them Dutch.

International investigators on Wednesday charged three Russians and a Ukrainian with murder over the shooting down of the plane, which was traveling between Amsterdam and Kuala Lumpur.

The incident forced airlines on the busy Europe-Asia route to divert flights away from Ukraine airspace.

Responding to the latest tensions over Iran, Malaysia Airlines said it "is closely monitoring the situation and is guided by various assessments including security reports and NOTAMs by respective airspace control authorities".

Australia's flag carrier Qantas said: "We're adjusting our flight paths over the Middle East to avoid the Strait of Hormuz and Gulf of Oman until further notice."

Singapore Airlines echoed Qantas and the other long-haul operators transiting over Iran, saying that some of its "flights may be taking slightly longer routings to avoid the affected Strait of Hormuz area".

"Singapore Airlines only chooses routes that are safe and have been cleared for use by the authorities. We will continue to monitor the situation closely," it said.

Europe-Asia flights have already faced disruption since February, when Pakistan restricted large swathes of airspace near its eastern border with India due to military clashes which came close to all-out war between the nuclear-armed rivals.

"This (Pakistan's action) has also pushed much of the transiting traffic south, nearer to the area now prohibited to US carriers," the flight-tracking website Flightradar24 said in a blog. — Agencies