National prosecuting departments have identified nearly 4,300 suspects who have been illegally detained for more than three years without being prosecuted or sentenced, the Supreme People's Procuratorate said on Monday.

"Such illegal detention has seriously harmed the defendants' rights and damaged the image and credibility of judicial authorities," said a senior official at the Supreme People's Procuratorate who declined to be named.

The maximum allowable detention time for the suspects is seven months, and prosecuting departments must prosecute suspects within six months.

The detained suspects were involved in more than 1,700 cases.

In April 2013, the Supreme People's Procuratorate identified more than 4,400 suspects who had been illegally detained for more than three years. About 95 percent of those cases were eventually cleared, with prosecuting departments deciding not to prosecute 10 suspects and the courts declaring 32 suspects innocent.

The court processes were sped up in the other cases.

According to the Criminal Procedure Law, suspects can be detained by police for interrogation. After enough evidence is obtained, they are transferred to prosecuting departments for further investigation. If prosecuting departments identify enough evidence, they will send the suspects to the courts.

"If police authorities or prosecuting departments can't conclude the cases within a certain period of time due to the complexity of such cases, weak investigative capabilities or not obtaining solid evidence, they will detain them for a long time, even for several years," said Hong Daode, a professor from China University of Political Science and Law.

"Many law enforcement officers abuse their powers and illegally detain suspects, and sometimes they abuse suspects and use torture to force them to confess," Hong said.

The new Criminal Procedure Law, which took effect in January 2013, stipulates that law enforcement authorities should protect human rights and other legitimate rights of the offenders.

In March 2013, judicial agencies were required to clear up cases involving illegal detention over three years and speed up judicial processes.

Prosecuting departments must enhance their supervisory roles of the police and courts to prevent similar cases, Hong said.

"If the prosecuting departments and courts discover illegal or inadequate evidence, they should immediately decide to set the suspects free rather than illegally detain them," he said.