Borussia Dortmund sign midfielder Axel Witsel from Tianjin Quanjian

Borussia Dortmund have agreed a deal for the transfer of midfielder Axel Witsel from Chinese Super League side Tianjin Quanjian, with the Belgium international becoming their seventh new arrival of the summer.

Dortmund's interest in Witsel was first reported by Funke Media last month, but Tianjin claimed a €20 million release clause in his contract could not be triggered because the Chinese transfer window had closed.

However, FIFA rules allow clubs from other countries to sign players until the end of their own domestic windows.

"It was my goal to return to Europe from China after the World Cup," Witsel said. "I am happy and also proud to be able to play for BVB. I didn't need much time after our first talks.

"Borussia Dortmund to me are one of the best clubs on the mainland [Europe]. To be honest, I can't wait to play in front of 81,000."

Witsel, who made six appearances for Belgium at the World Cup as they finished third, has won a total of 96 caps.

"We were strongly interested in signing Axel Witsel for the past few months," Dortmund sporting director Michael Zorc said. "We are delighted he opted to join Borussia Dortmund.

"Axel is a player with huge international experience. He has the skill set to shape our midfield: Tactical understanding, good in the direct duels, pace, creativity and mentality."

New Dortmund coach Lucien Favre has already signed keepers Marwin Hitz and Eric Oelschlagel, defenders Abdou Diallo and Achraf Hakimi, holding midfielder Thomas Delaney and winger Marius Wolf.

Meanwhile, Dortmund midfielder Julian Weigl faces an uncertain future following Witsel's arrival and has been linked with clubs in both the Premier League and La Liga.

There is disappointment in Tianjin at Witsel's departure. He had been due to return from his post-World Cup break on Aug. 5 and Tianjin coach Paulo Sousa, as well as others at the club, consistently said that they expected the Belgian back on that date.

The 29-year-old arrived in January 2017 and impressed as he helped the newly-promoted club to a third-place finish and a first qualification for the AFC Champions League.

He leaves at a bad time. The port city side have slid down to seventh after losing three of their last four league games. Tianjin have also lost a growing number of players due to injury and suspension and, with the Chinese transfer window already closed, are unable to sign any replacements.

Not only that, the first leg of the Champions League quarterfinal against Japan's Kashima Antlers takes place in late August.

ESPN FC's Asia correspondent John Duerden contributed to this report