Northern Ireland is on critical terror alert following three attacks in London and Glasgow in recent days.
A burning car crashed into Glasgow Airport
New NI Secretary Shaun Woodward said the threat level was the same across the UK - the highest of five states of alert in a system introduced last year.
Calling for vigilance, he said: "We are taking all the appropriate steps to protect people in Northern Ireland."
Security was stepped up at Belfast's two airports following the Glasgow airport attack.
Passengers flying to Glasgow with Flybe from George Best Belfast City Airport have been told to check in earlier due to increased security.
Belfast International Airport advised customers to check with Easyjet about Glasgow arrivals and departures.
Mr Woodward said times had changed as, in the past, any references to terrorism in Britain were "absolutely specific to Northern Ireland".
"Today when we talk about this - and it's a bizarre thing to talk about in the context of being normal - terrorism by and large in Northern Ireland is actually the problem which we all face throughout the UK.
"It is the threat from al-Qaeda and related terrorist groups who want to disrupt our British way of life - we are not going to let that happen."