According to Reuters, China authorities asked Apple to close its iTunes movies and iBooks stores in China last Friday, on the basis of the Regulations on the Administration of Online Publishing Services, which came into effect on March 10. According to article 10 of this regulation:
Sino-foreign joint ventures, Sino-foreign cooperation and foreign-funded enterprises shall not engage in online publishing services. Network publishing service units shall report to the State Administration of Press, Publication, Radio, Film and Television for approval in advance to carry out project cooperation with domestic Sino-foreign joint ventures, Sino-foreign cooperation, foreign-funded enterprises or overseas organizations and individuals.
After the service was suspended, Apple officials also responded. An Apple spokesperson said: We hope to reopen movies and bookstores to users in China as soon as possible.