CAIRO, June 29 (Reuters) - A court on Tuesday postponed to Sept. 25 a session to hear closing arguments in the murder case retrial of Egyptian property tycoon and politician Hesham Talaat Moustafa because of a lawyer labour dispute.

The retrial of Moustafa, a member of parliament for Egypt's ruling party and former chairman of Talaat Moustafa Group TMGH.CA, was ordered after an appeal court cited flaws in his original conviction over the murder of a Lebanese singer.

Moustafa and security man, Muhsen el-Sukkari, were sentenced to death after the original guilty verdict in a trial that gripped the Arab world and rattled shares in Moustafa’s firm.

This trial and others have been disrupted by a row between lawyers and judges after a court sentenced two lawyers to five years in prison for assaulting an Egyptian attorney during an investigation session.

The lawyers’ syndicate has coordinated protests, including calls for members to boycott court sessions.

“There is a public protest and the court has postponed the case. I am bound to follow the syndicate’s decision,” Moustafa’s lawyer Farid el-Dib told Reuters.

The court said the next hearing would be on Sept. 25.

Moustafa and Sukkari were arrested in 2008 over the murder of singer Suzanne Tamim in Dubai that year. They were found guilty by a criminal court in May 2009, a ruling that surprised Egyptians who usually regard the elite to be above the law.

Media described the murder as an act of revenge after Tamim ended an extramarital affair with Moustafa.

The retrial, which started on April 26, was granted on the grounds of legal errors and after the original court was found to have failed to respond to defence requests. (Writing by Yasmine Saleh, editing by Edmund Blair)