BERLIN (Reuters) - Germany’s top appeal court has partially overturned the conviction of a former Rwandan rebel group leader for abetting war crimes in the Democratic Republic of Congo, citing a lack of evidence and referring it to a different court.

A court in Stuttgart had in 2015 sentenced Ignace Murwanashyaka to 13 years in prison for assisting in war crimes. He became president of the ethnic Hutu FDLR (Democratic Forces for the Liberation of Rwanda) group in 2001.

The FDLR fled to Congo after the 1994 Rwandan genocide in which 800,000 ethnic Tutsis were killed.

The FDLR played a major role in Congo’s 1998-2003 conflict, in which 5 million people died, and has continued mass rapes, torture and killing in the east of the country, according to civil society groups.

Murwanashyaka, who grew up in Rwanda but has lived in Germany since the 1980s was arrested in 2009. From Germany, he acted as the FDLR’s top international representative while coordinating its activities and was in contact with the group’s political and military leadership in Rwanda.

The original trial, which lasted four years, was possible under a German law allowing German courts to try people for crimes committed abroad.

The appeals court in Karlsruhe said the verdict required serious legal consideration.

“It is not substantiated or proven that the accused objectively ... supported or facilitated the crimes that the (Stuttgart) court viewed as premeditated behaviour,” said the appeals court.

Specifically, Murwanashyaka had been convicted of the premeditated abetting of several attacks on Congolese settlements in 2008 and 2009 in which numerous civilians were killed and many houses were burned, said the court.

He made available telephones and equipment for satellite phones for military use.

A different court will now have to consider the case again and decide whether he abetted war crimes and he may have his sentenced reduced.

The appeals court did, however, uphold Murwanashyaka’s conviction as being a ringleader of a terrorist organization.

It also upheld the conviction of his deputy, Straton Musoni, who had been sentenced to eight years behind bars for being a ringleader of a terrorist organization.