Barack Obama left the owner of a streetside restaurant in Vietnam "stunned" when he stopped off there for a $6 meal.

The US president ate at Bun Cha Huong Lien in the Vietnamese capital of Hanoi, along with celebrity chef Anthony Bourdain.

He popped into the restaurant on an official visit to the country, after announcing that the US is lifting an ban on arms sales to Vietnam.

The pair ate pho - a traditional Vietnamese soup served with sauces on the side - a plate of greens, two appetizers and also had a beer each.

Restaurant owner Nguyen Thi Lien was aware a foreign television crew was coming to the restaurant, but did not know that Obama would be coming.

She told AFP news agency that she was shocked when the US president arrived.

US Secret Service and local police closed down the streets surrounding the restaurant on Monday evening.

Anthony Bourdain posted on Twitter that he paid for the bill for the meals that the pair ate.

A large crowd gathered to see Obama leave the Bun Cha Huong Lien eatery.

Obama will appear on an upcoming episode of Anthony Bourdain: Parts Unknown on CNN, where the chef dines at local places around the world.