BERLIN (AP) — Artist Ai Weiwei said in an interview published Wednesday that Chinese authorities returned his passport with almost no strings attached and promised him he can return to China.

Ai traveled to Munich last week after having his passport returned, four years after it was confiscated, for a medical checkup and to see his young son. In an interview with the Munich-based daily Sueddeutsche Zeitung published on Wednesday, the dissident artist said Chinese authorities now have a more positive attitude toward him.

"They know that I want to make China into a better country, that I am concerned about the young generation," he was quoted as saying. "There is a basis of trust, otherwise they would not allow me, the former enemy of the state, my exhibitions; otherwise they would not have returned my passport."

Asked under what conditions his passport was returned, he replied that "there were almost none," without elaborating. "They promised that I could come back, which was very important to me. They said, 'you are a free person.'"

Ai said that an anti-corruption campaign by President Xi Jinping is creating "enormous tension," with authorities keen not to lose control and intervening at the smallest sign of unrest, the Sueddeutsche Zeitung reported. But he added that "this campaign was really necessary."

Ai also said that he has to be cautious and work with the situation — "that is much more difficult than vilifying opponents." He also said that he wants "not just to criticize but to offer solutions."

He didn't detail his future plans.