Before starting his first address before the United Nations General Assembly, El Salvador President Nayib Bukele asked the audience to hold on a second, took out his phone, and snapped a selfie.

"Believe me, many more people will see this selfie than will hear this speech," the 38-year-old quipped before delivering his address calling on the United Nations to change with the times and for world leaders to do more to connect with their countries' youth.

The former mayor of the capital, San Salvador, who took office in June, is a prolific user of social media.

In his speech, he attributed his election victory to his mastery of platforms like Facebook Live, which he said his political opponents did not fully grasp.

After finishing his speech, Mr Bukele uploaded the photo to Twitter, where it received more than 7,000 likes in less than an hour.

The picture showed him smiling in front of the UN logo - a map of the world surrounded by olive branches - and Argentine UN Ambassador Martin Garcia Moritan, one of several General Assembly vice presidents.

"Maybe in a few years, thousands of us will not have to travel to New York to meet in this building," Mr Bukele said.

"A series of video conferences would have cost several hundred million dollars less, and I'm sure it would have the same effect, if not greater."