UN Secretary-General Antonio Guterres made the comment to reporters after talks with Saudi King Salman, Crown Prince and Interior Minister Mohammed bin Nayef, and Deputy Crown Prince Mohammed bin Salman.
"One of the things that fuel terrorism is the expression in some parts of the world of Islamophobic feelings and Islamophobic policies and Islamophobic hate speeches," Guterres said at a joint news conference with Saudi Foreign Minister Adel al-Jubeir.
"This is the best support that Daesh can have to make its own propaganda," Guterres said, using an Arabic acronym for the Islamic State group of Sunni extremists in Syria and Iraq.
The terrorist group has also claimed deadly attacks in Saudi Arabia and in Europe.
Anti-immigration politicians including France's Marine Le Pen have seen their popularity rise after an influx to Europe of migrants, many of them Muslims fleeing wars in Syria and elsewhere.
US President Donald Trump issued an order in late January that denied entry to all refugees for 120 days.
It also blocked travellers from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen for 90 days. Refugees from Syria were blocked indefinitely.
Syria's conflict has created 4.8 million refugees and killed more than 310,000 people since it began with anti-government protests in March 2011.
Mr Guterres said "we will never be successful in fighting terrorism in Syria if an inclusive political solution is not found for the Syrian people."
A new round of UN-sponsored peace talks is scheduled for February 20 in Geneva.
Guterres arrived in Saudi Arabia from Turkey and is to be in Dubai on Monday for the World Government Summit during his regional tour.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)