Bahrain has released radar footage which it said showed Qatari fighter jets passing by two Emirati commercial airliners on their way to the island nation.
The two alleged fly-bys have triggered a new dispute between the Gulf nations amid the diplomatic crisis gripping Qatar.
The incidents could further escalate tensions between Qatar and four Arab nations which have been boycotting it for months, among them the United Arab Emirates, home to the world’s busiest international airport.
They also could affect long-haul airline travel, as the region’s carriers are a crucial link between the East and West.
Emirati officials described the fly-bys as the fighter jets "intercepting" their civilian aircraft.
Qatari authorities denied their jets intercepted the aircraft and have dismissed footage as "unauthenticated videos".
The UAE’s allegations follow two complaints by Qatar to the United Nations about Emirati military aircraft allegedly violating its international airspace amid the diplomatic crisis. The UAE denies those allegations.
Bahrain state television aired radar footage which it described as showing Emirates flight No EK837 from Dubai flying toward Bahrain International Airport at 10,400ft.
Two other radar signals described by the broadcaster as Qatari fighter jets flew at around 8,500ft in front of the Emirates flight. The radar screen briefly flashes orange text, likely a collision warning.
It is not clear from the footage at what distance the fighter jets allegedly passed the Emirates flight, but Bahrain previously described the distance as being about two miles.
The broadcaster also aired footage of an aeronautical chart it said showed a Qatari fighter jet flying across the flight path of a just-passed Etihad airliner, both at 8,000ft. It identified the flight as ETD23B, which corresponds to Flight No EY371, a direct Abu Dhabi-Bahrain flight which took off on Monday morning.
Both Dubai-based Emirates and Abu Dhabi-based Etihad have declined to comment. Both flights flew in international waters just north of the tip of Qatar, a peninsular nation that juts into the Persian Gulf, before landing in nearby Bahrain.
Saif al-Suwaidi, the director-general of the UAE’s civil aviation division, told state media that crew and passengers on board the flights saw the military aircraft.
The incidents "constituted a clear and explicit threat to the lives of innocent civilians," he said.
Qatar’s government communication office dismissed the Bahrain state television report as part of a "smear campaign" against it by the UAE.
Qatar’s stock exchange dropped some 2.5% in trading on Monday, one of its biggest jolts since the crisis began.
Bahrain, Egypt, Saudi Arabia and the UAE cut off Qatar’s land, sea and air routes on June 5 over its alleged support for extremists and its close ties with Iran.
Qatar has long denied funding extremists. It recently restored full diplomatic relations with Iran, with which it shares a massive offshore natural gas field that makes the country and its 250,000 citizens extremely wealthy.
The crisis has hurt Qatar Airways, Doha’s long-haul carrier which competes with Emirates and Etihad.