'We Will Never Let these Terrorists Win,' Vows Cameron after Brussels Attacks

British Prime Minister David Cameron condemned the "appalling" attacks in Brussels and said Europe should stand together against the terror threat, following an emergency cabinet meeting in London on Tuesday.

"We will never let these terrorists win," Cameron said at his Downing Street office.

"We face a very real terrorist threat right across the different countries of Europe and we have to meet that with everything we have."

Britain's counter-terror chief Mark Rowley earlier said police numbers would be stepped up at transport hubs following three explosions at Brussels airport and a city metro station which killed at least 26 people.

Cameron said he had spoken to his Belgian counterpart Charles Michel to express his condolences.

"We absolutely stand with them at this very difficult time," he said.

"These were attacks in Belgium; they could just as well be attacks in Britain.

"These are difficult times, these are appalling terrorists but we must stand together to do everything we can to stop them and to make sure that although they attack our way of life and they attack us because of who we are, we will never let them win."

Cameron recalled the July 7, 2005 Islamist terror attacks on London's transport system, in which 52 people died.

"What we should be doing today is expressing our sympathies and condolences with the people in Belgium who've suffered this appalling terrorist attack," he said.

"We in this country know what that feels like because of what we experienced in 7/7."

London's Gatwick airport stepped up security on Tuesday after a string of explosions in Brussels.

"As a result of the terrible incidents in Brussels, we have increased our security presence and patrols around the airport," the airport said in a statement.

Cameron earlier said on Twitter he was "shocked and concerned" by the events in Brussels.

A string of explosions rocked Brussels airport and a city metro station on Tuesday, killing at least 30 people, according to firefighters, as Belgium raised its terror threat to the maximum level.

Eurostar trains to Brussels from London's St. Pancras station have been suspended.

London's Heathrow, Europe's busiest airport, would not confirm it was stepping up security but said it was "working with the police at Heathrow who are providing a high visibility presence."