China's best-known film director Zhang Yimou has paid 7.5 million yuan ($1.2 million) for violating the one-child policy, officials said Friday, closing a case that had attracted widespread attention.

Following months of rumours that he had fathered up to seven children with different women, Zhang admitted in December he has two sons and a daughter with his current wife, Chen Ting, all from before they were married. He also has a daughter with a previous wife.

The family-planning law, implemented in the late 1970s in a bid to prevent over-population, restricts most parents to one child.

Critics say the law is enforced unevenly and sometimes aggressively, with wealthy and well-connected families better able to pay fines levied for extra children.

"The Binhu district family planning bureau received through bank transfer Chen Ting and Zhang Yimou's payment of 7,487,854 yuan," the district government said through its verified social media account.

The district is part of Chen's hometown of eastern Wuxi city.

The case took nine teams more than six months to investigate and the couple's unwillingness to cooperate was said to have hampered the probes, Binhu authorities said earlier.

They added that the penalty was based largely on the couple's income in the years before each child was born.

The director has said his income varies, and in one year only totalled $450 - under 3,000 yuan.

The fine far exceeded most of those handed to violators of the one-child policy, but fell far below the 160 million yuan speculated in previous Chinese media reports.

Exceptions to China's one-policy limit include some rural families whose first child is a girl, ethnic minorities, and couples in which at least one is an only child.