WASHINGTON - President Donald Trump said Friday that the Islamic State group will pay a "big price" for every attack it stages against the United States, following the New York truck attack by an IS loyalist.

The US military has hit IS "much harder" over the past two days after the jihadist group claimed the attacker was one of their soldiers, Trump said.

"They will pay a big price for every attack on us!" Trump wrote on Twitter.

The New York attack Tuesday left eight dead and 12 wounded. (AFP)