LONDON -- Britain scrambled fighter jets Friday to intercept a commercial airliner carrying more than 300 people from Pakistan, diverting it to an isolated runway at an airport on the outskirts of London and arresting two British passengers who allegedly threatened to destroy the plane.

A British security official said the situation involving the Pakistan International Airlines flight did not appear terror-related, though police were still investigating, but the incident further rattled the U.K. just days after a soldier was killed on a London street in a suspected terror attack.

The security official requested anonymity because he was not authorized to discuss the investigation.

A Pakistani official briefed by British police and PIA security on the investigation said the two suspects, speaking Urdu, allegedly threatened to "destroy the plane" after an argument with crew. The official spoke on condition of anonymity because he was not authorized to speak about the case on the record.

Flight P709 was traveling from Lahore, Pakistan, to Manchester Airport when it was diverted by the fighter jets to Stansted Airport. The U.K. Ministry of Defense confirmed that Typhoon jets were launched to investigate an incident involving a civilian aircraft but gave no further details.

Passenger Nauman Rizvi told Pakistan's GEO TV that two men who had tried to move toward the cockpit during the flight were handcuffed and arrested once the plane landed. Rizvi said that after the men were taken away, the flight crew told passengers there had been a terrorist threat and that the pilot had raised an alarm.

Essex Police said they were notified at 1:20 p.m. local time (12:20 GMT, 8:20 a.m. EDT) that a threat had been made to an aircraft. The force said that after the Boeing 777 landed at 2:15 p.m., armed officers entered it and arrested two British nationals, aged 30 and 41, on suspicion of endangering the aircraft.

The suspects were taken to a police station where they face questioning, the police said in a statement. The plane will be examined by forensic specialists but no suspicious items have been recovered so far, police added.

"This incident is being treated as a criminal offense," the police statement said, in another indication it was not being seen as a terror case.

Mashood Tajwar, a spokesman for PIA, said 297 passengers and 11 crew members were on the plane. By late afternoon Friday, passengers had disembarked from the plane and were being interviewed, according to Mark Davison, a spokesman for Stansted Airport.

Police across Britain have stepped up patrols in recent days following the suspected terror attack in south London.

Two men with a meat cleaver and knives attacked and killed a British soldier in broad daylight, and gruesome footage that emerged after the attack showed one of the alleged assailants angrily complaining about the British government and troops in foreign lands.

Those two suspects were shot when police arrived on the scene and have been hospitalized.

___

Associated Press writers Paisley Dodds in London and Zarar Khan in Islamabad contributed to this report.

Also on HuffPost:

Loading Slideshow...
  • An Indian Muslim devotee prays at the shrine of Sufi saint Khwaja Moinuddin Chishti during the Urs festival, in Ajmer, India, Friday, May 17, 2013. (AP Photo/Altaf Qadri)

  • In this photo provided by the Vatican newspaper L'Osservatore Romano, Pope Francis frees a dove during his weekly general audience in St. Peter Square at the Vatican, Wednesday, May 15, 2013. (AP Photo/L'Osservatore Romano, ho)

  • Marcelo Bastos of Brasil warms up prior to the Skateboard Vert Final at the Montjuic Pool during the X-Games Barcelona day 1 on May 16, 2013 in Barcelona, Spain. (Photo by David Ramos/Getty Images)

  • An Afghan man jumps from a diving board into a swimming pool on a hill overlooking Kabul, Afghanistan, Friday, May 17, 2013. (AP Photo/Anja Niedringhaus)

  • Borneo apes play in their enclosure on May 16, 2013 at the zoo in Gelsenkirchen, western Germany. (PATRIK STOLLARZ/AFP/Getty Images)

  • A child march with his father, a reservist of Paraguay's Army, during Independence Day parade in Asuncion, Paraguay, Tuesday, May 14, 2013. (AP Photo/Jorge Saenz)

  • In this Sunday, May 12, 2013 photo, an Indian Muslim Sufi devotee is squashed between others during a procession at the shrine of Khwaja Moinuddin Chishti during the Urs festival in Ajmer, India. (AP Photo/Kevin Frayer)

  • Guests of the Marina Bay Sands hotel in Singapore look over the city-state's financial district from a rooftop swimming pool on May 13, 2013. (ROSLAN RAHMAN/AFP/Getty Images)

  • An Afghan National Police officer mans a checkpoint on the outskirts of Maidan Shahr, Wardak province, Wednesday, May 15, 2013. (AP Photo/Anja Niedringhaus)

  • A Palestinian refugee boy walks at alley in front of his home, during the 65th anniversary of "Nakba", Arabic for catastrophe, the term used to mark the events leading to Israel's founding in 1948, at Shati refugee camp in Gaza City, Monday, May 13, 2013. Arabic on the wall reads, "we will return." (AP Photo/Adel Hana)