Foreign Secretary Yvette Cooper indicated that 102,000 British nationals have registered their presence in the region.
She said a total of about 300,000 British citizens are in Gulf countries targeted by Iran.
British nationals are being advised to follow the instructions of local authorities and monitor the Foreign Office’s travel advice, which officials expect to change rapidly.
Those in Bahrain, Israel, Kuwait, Palestine, Qatar and the United Arab Emirates (UAE) have been urged to register their presence with the Foreign Office online.
The Government has used the registration scheme before to provide urgent updates to people affected by international crises, but it has not previously needed to deal with so many people in so many different countries.
Ms Cooper told BBC Breakfast: “The latest figure I have from this morning is we have 102,000 people (who) have responded to our proposal to ask people to register their presence so we know where they are, particularly in these Gulf countries that have been targeted so we know where they are and so that we can get them rapid information.
“In many of these countries the airspace is currently closed because of the Iranian attacks.
“This is deeply stressful obviously for people because we’re talking about a lot of people who are holidaymakers, who were transit passengers just passing through or people on business visits to the region and who we want to make sure can get safely home.”
Many commercial flights in the Middle East have been grounded since the attacks began on Saturday.
Nearly half of the flights scheduled to depart from London Heathrow to the region on Sunday were cancelled.
Analytics company Cirium said 24 of the 56 flights from the UK’s busiest airport were axed.
British Airways said it is “closely monitoring the situation” and has cancelled “a number of our flights to the Middle East”.
Virgin Atlantic axed two flights to Heathrow on Monday – one from each of Dubai, UAE and Riyadh, Saudi Arabia – while others were rerouted.
Qatar Airways said on Monday morning that all its flights remain suspended.
