Two Turkish opposition journalists who were handed jail sentences in a hugely-controversial espionage case earlier this year went on trial again Wednesday over alleged ties to the group accused of planning the July coup, local media reported.

Former Cumhuriyet editor-in-chief Can Dundar and the newspaper's Ankara bureau chief Erdem Gul were sentenced in May to five years for allegedly revealing state secrets in a story published a year earlier.

Both men are currently appealing the verdict which related to a story about Turkey allegedly smuggling arms to Syrian rebels that infuriated President Recep Tayyip Erdogan who warned Dundar he would "pay a heavy price" for it.

They were allowed to go free pending the appeal.

Dundar, who fled Turkey and is believed to live in Germany, was not present for the hearing, but his wife, Dilek Dundar, and Gul appeared at the Istanbul court to hear new charges of "knowingly and willingly" helping the movement led by Fethullah Gulen, despite not being a member, Dogan news agency reported.

The charges relate to accusations the two men received some of their information for the story from the Gulen movement.

If found guilty, they could face up to 30 years in jail.

At the hearing, the pair's lawyers called for them to be acquitted, the agency said.

The trial was adjourned until November 16.

A reclusive cleric who lives in self-imposed exile in the United States, Gulen has been accused by Ankara of running a "terrorist" organisation and ordering the failed putsch to oust Erdogan.

He has repeatedly denied the allegations.

Following the attempted coup, Turkey declared a state of emergency which remains in force.

Dundar has said he will not appear before the judiciary while there is a state of emergency, saying it would result in an unfair hearing.

He has also complained that his wife has been held "hostage" by the authorities who cancelled her passport after he left the country.