A terminal at Heathrow has been evacuated due to a 'security alert' with armed police on the scene.
Passengers have reported their flights being held up amid the issue at Terminal 4, with the airport's station also closed.
One person on X (formerly Twitter) said: "I'm on a plane being held at the gate at Terminal 4 due to a 'security incident'."
Another said: "Heathrow Terminal 4 has been evacuated due to a terror suspect. Armed police are on the scene; if you have urgent business there, you cannot enter."
Transport for London (TfL) wrote on X: "Heathrow Terminal 4 station. This station is closed while we respond to a security alert. Tickets are being accepted on London Buses via any reasonable route."
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A Heathrow spokesperson said: "Police responded to a suspicious package earlier today. The situation has been resolved...The airport is operating normally now."
The whole incident is understood to have only lasted 20 minutes.
A Met Police spokesperson said: "It was a suspicious bag, we attended, full stand down. No terror suspect."
The Terminal and station have now re-opened.