The city of Kyoto signed a contract to pay 1 million yen ($9,200) to a comedy duo to promote the city on Twitter, local officials revealed Monday, but the city is coming under fire after the pair posted messages without marking them as being promotional.

The two brothers, who form the duo "Miki," made several posts in October 2018, but the tweets did not mention the relationship between the city and their agency Yoshimoto Kogyo Co.

The agreement, signed in fiscal 2018 by the city and the agency, which changed its name in June from Yoshimoto Creative Agency, was part of a larger promotional package whereby the city government would pay 4.2 million yen for the agency to form a group of artists to promote the city's cultural events.

Their twitter posts included mentions of the city-run subway and the Kyoto International Film and Art Festival.

"Anyone who loves Kyoto can support the city of Kyoto!" said one of the tweets with a link to the city's "hometown tax" donation program.

A city official said it decided to use social media to drive interest among young people as the local government had been having difficulty delivering information about the city to the demographic.

"We did not do it with the intent to confuse people by trying to make something seem more valuable than it is," a city official said.

The official also said that the relationship between the comedians and the city was clear since the posts hashtagged the name of the group that had been specially formed by the talent agency to promote the city.

"It is crucial to make it obvious that a tweet is a product placement" when it is posted for a promotional purpose, said Makiko Kawakita, a Nanzan University professor and an expert in consumer trends and public relations. "If you are getting money for product placement by companies and tweeting without divulging the relationship, consumers may get the wrong impression."

She also said that artists should be more aware of the impact of social media and that if they are not careful, their image may be negatively impacted.

"Influencer marketing can be an effective tool for municipal governments," said Michio Kitamura, a professor of Hokkaido University, versed in municipal public relations. "But as a rule, it is imperative to make it obvious when a tweet (as part of influencer marketing) is product placement."

Kitamura also said 1 million yen for the two men to tweet a few lines twice each seems "extremely expensive" and "out of touch with the general public."

The city said that it believes the cost to be "appropriate," while the company declined to comment.