Washington: US President Donald Trump on Thursday condemned the Paris terrorist attack, saying there is a need to stay strong and vigilant.

"First of all, our condolences from our country to the people of France. Again, it is happening, it seems...It is a very, very terrible thing that's going on in the world today," Trump told reporters in a joint press conference with visiting Italian Prime Minister Palo Gentiloni.

"But it looks like another terrorist attack. And what can you say -- it just never ends. We have to be strong and we have to be vigilant. And I have been saying it for a long time," Trump said in response to a question as he was joined by Gentiloni in condemning the attack.

"Allow me to join President Trump's words for what happened in Paris. These words of condolences and closeness to the French people. And this is a very delicate period for them, just three days before the election," the Italian prime minister said.