SINGAPORE - The shootings in Copenhagen show that even a city on alert remains vulnerable to terrorist attacks, said Deputy Prime Minister Teo Chee Hean on Sunday morning.

"You can see that even in a city on high alert, it is very difficult to stop all attacks, because all it needs is one person," he said on the sidelines of a community event in Pasir Ris.

Mr Teo, who is also the Home Affairs Minister, added that the community must stay united in the face of such attacks to prevent terrorism from achieving its goals.

"Terrorists want to achieve two things - to terrorise people so that they can't continue with their daily lives, and also to split communities."