Congolese former rebel leader Bosco Ntaganda has ended an unprecedented hunger strike in his detention cell in The Netherlands after a two-week standoff with the judges at his war crimes trial.

"He has begun to eat again," his lawyer Stephane Bourgon told AFP, adding Ntaganda had decided to end his self-imposed fast late Tuesday after the court granted him some concessions.

The once-feared rebel leader from the Democratic Republic of Congo is on trial at the International Criminal Court where he has denied 18 charges of war crimes and crimes against humanity.

But saying he was "ready to die", Ntaganda had decided to refuse food "in the ultimate act of protest" according to his lawyer, after judges maintained tight restrictions on his visitors saying they feared he might tamper with witnesses.

Bourgon told AFP "we won permission to appeal the judges' decision and we have made arrangements so that he can see his wife, this week, with a certain degree of intimacy."

Ntaganda, who has not appeared in the courtroom in The Hague since September 7, has also begun instructing his legal defence team again, Bourgon said.

"He is weak, and has lost weight and you can see it in his face. But there is nothing to be alarmed about," added Bourgon.

Ntaganda was however again not present when his trial resumed on Wednesday afternoon, and the judges granted him permission not to attend the trial in person again until September 29 so he can profit from the visit of his family.

But Bourgon told AFP that for Ntaganda, born in 1972, the "fight is far from over as he wants to prove he is innocent of the accusations of interfering with witnesses."

"The restrictions are just the consequence of the allegations which we believe have been evaluated on an insufficient basis by the judges. These allegations could impact the trial because they concern witnesses who have already testified, or who will do so."

Once dubbed "The Terminator", Ntaganda has denied the charges arising out of savage ethnic attacks carried out in the DR Congo by his rebel Patriotic Forces for the Liberation of Congo (FPLC) in 2002-2003.

His trial opened in September 2015 after he walked into the US embassy in Kigali in 2013.

The eastern Democratic Republic of Congo has been mired for two decades in ethnically-charged wars, as rebels battle for control of its rich mineral resources.

Prosecutors say Ntaganda played a central role in the Ituri conflict in the far northeast which rights groups believe alone has left some 60,000 dead since 1999.