The UAE on Monday said that Qatari fighter jets intercepted two of its commercial airliners in international airspace on the way to Bahrain.

The incident could further escalate tensions between Qatar and the four Arab nations that have been boycotting it for months, among them the UAE, home to the world's busiest international airport.

It follows two complaints by Qatar to the United Nations about Emirati military aircraft allegedly violating its international airspace amid the diplomatic crisis.

The WAM news agency reported the violations on Monday, citing the country's General Civil Aviation Authority (GCAA).

"The GCAA received a message from one of the UAE's national carriers on Monday morning that one of its aircraft on a flight to Manama on a normal route had been intercepted by Qatari fighters," the report said. "The flight was a regular, scheduled service on a known flight-path that met all the required and internationally recognised approvals and permits," it said.

It later said a second flight to Bahrain was similarly intercepted.

The GCAA regarded this incident as "a renewed breach of international laws and conventions, and a flagrant and serious threat to the safety of civil aviation".

The authority is examining legal options available to it via the International Civil Aviation Organisation and other relevant bodies.

Sheikh Saif bin Ahmed Al Thani, Qatari government spokesman, denied the UAE's claim on Twitter.

The UAE is home to two major national carriers, Abu Dhabi-based Etihad and Dubai-based Emirates.

Both airlines declined to comment, though Bahrain's Foreign Ministry identified one of the affected aircraft as Emirates flight No EK837.

That flight left Dubai at 8.20am on Monday and landed 46 minutes later, flying out over international waters near the northern tip of Qatar, before arriving in Bahrain. That's been the standard route of all Emirati commercial airliners since the crisis began.

FlightRadar24, a popular airplane tracking website, did not show any unusual routes between the UAE and Bahrain. "There appears to be no deviation from standard routing and approach patterns in today's flights," FlightRadar24 spokesman Ian Petchenik said.

Qatar's stock exchange dropped some 2.5 per cent in trading on Monday, one of its biggest jolts since the crisis began.

Bahrain strongly condemned the interception by Qatari fighter jets, stressing that this is a clear violation of relevant international conventions and laws, particularly those of the ICAO, and the provisions of the Chicago Convention on International Civil Aviation and its amendments of 1944.

"This rejected hostile behaviour by Qatar against civil aircraft has become frequent in recent times and jeopardises the safety of civil aviation and poses a threat to the lives of civilians," the Bahrain Foreign Ministry said in a statement.

"The Ministry of Foreign Affairs stresses the Kingdom of Bahrain's full support for the UAE and its backing for all of the measures it takes to maintain its security and stability, to stop these violations and to repel these breaches by the State of Qatar," the statement added.

Bahraini radars detected interception of UAE passenger flights
The UAE's General Civil Aviation Authority, GCAA, said that on Monday that the Bahraini radars detected the Qatari jets as they intercepted the UAE civilian flights.

"Moreover, the crews and passengers saw the incidents with their naked eyes, which proves that the interception posed a present and clear threat to the lives of innocent civilians," he said.

"The Qatari fighter jets intercepted the first plane at 10:30, while the second was intercepted at 11:05 while flying at 9,000 to 10,000 feet altitude in regular flights approved by the International Civil Aviation Organisation, ICAO," said Saif Al Suwaidi, Director-General of the GCAA.

Al Suwaidi said that the Qatari side had neither shown prior objection to the use of the aircraft's path nor issued a warning after the use of the path.

He described the act of Qatari fighter jets approaching the civilian UAE planes without warning as a flagrant violation of international laws, a threat to civil aviation safety, and a serious and unprecedented act of intimidation.