BERLIN — China may be regretting the decision to have its under-20 soccer team to play a series of friendlies against lower-level German clubs.

The Chinese team walked off the field during the first half of its game at fourth-division club TSV Schott Mainz last Saturday when a small group of spectators displayed Tibetan flags. The visiting players refused to continue for about 25 minutes until the flags were withdrawn. Players from the home side asked the protestors to remove the flags.

Reinhardt Grindel, the president of the German soccer federation, has defended supporters’ right to freedom of expression, while his own organization has faced criticism for organizing the matches in the first place.

China’s under-20 team next faces FSV Frankfurt on Saturday for the second friendly in its series of games against teams from the southwest division. The fall-out from the first encounter may encourage other fans to make their protests known.

“It has been made clear to the Chinese federation that when you play in Germany you also have to deal with the fact that anyone can express their opinion,” Grindel said this week.

The one-off series of games against teams in the fourth tier of Germany’s league system is the result of a five-year soccer partnership between the countries to help develop the game in China, but it has already led to a difference of opinion with a foreign ministry spokesman, Lu Kang, blasting the Tibetan flag action.

Lu said the country firmly opposed any “separatist, anti-China or terrorist activities” defending Tibet and called for “mutual respect” from Germany as host toward its guest.

China has controlled Tibet for more than half a century. It sent troops to occupy the Himalayan territory following the 1949 communist revolution and contends that the region has been part of Chinese territory for centuries. Many Tibetans claim a long history of independence under a series of Buddhist leaders. China established the Tibetan autonomous region in 1965.

Grindel did not directly address Lu’s comments, but said he would “be happy if the Chinese soccer federation concentrated on the chance for its under-20s to play friendly games at a good level.”

More protests are expected, if not in Frankfurt, then against Hoffenheim’s second team the following weekend, or Wormatia Worms the weekend after that.

However, the German federation has also been heavily criticized for inviting the Chinese to compete within the structure of the league system, with three teams – Waldhof Mannheim, Stuttgarter Kickers and TuS Koblenz – refusing to take part despite a 15,000-euro ($17,700) bonus for each side.

“The DFB’s excessive marketing of soccer must be stopped,” Mannheim fan representative Soeren Runke said in an open letter from fans to German federation vice president Ronny Zimmermann in July, after the series of games was approved.

The letter blasted the federation for pursuing its own interests without taking the clubs into account.

“The federation sees itself on a higher level than the individual clubs,” the letter said. “It dictates instead of discussing, creates facts instead of listening, and focuses on the benefits for itself, rather than its members, the basis of its own institution.”

China’s under-20 team was invited to play the friendlies on free match-days made possible because of an uneven number of teams in the league. Sixteen of the 19 teams are participating in the one-off action, which allows China’s under-20 team to prepare for the 2020 Olympics in Tokyo.

Christoph Radtke, the chairman of FK Pirmasens, which was one of six teams relegated from the four-tier league despite finishing 14th last season, told newspaper Die Zeit in an interview that the action was “pure capitalism” on behalf of the federation.

Pirmasens had appealed to keep an even number of teams in the league, also to prevent its own under-23 side from being automatically relegated from the league below.

“But instead of keeping us, money from China is being chosen. A horror story,” Radtke said.

Other sides saw it the same way.

“This is a resounding slap in the face for all soccer fans,” Steffen Vahldiek, the chairman of fifth-tier club FSV Bissingen, told the Heilbronner Stimme newspaper. “The question is: Is it about a 20th team or the money for the DFB?”