ANKARA, Turkey (AP) — Sixteen people went on trial in Istanbul on Tuesday, charged with “political and military” espionage on behalf of Israel, Turkish media reports said.

The defendants, including Palestinians and Syrians, were arrested in October in an operation by Turkey’s national intelligence agency, MIT, according to the pro-government Sabah newspaper and other Turkish media. They face up to 20 years in prison if convicted.

The suspects allegedly spied on Palestinian and Turkish students and other people on behalf of Israel, operating in five separate groups, Sabah newspaper reported. Some of the suspects allegedly met with Israeli officials in Switzerland, Croatia, Romania and Kenya.

Turkish intelligence officers reportedly monitored the group for a year before they were arrested.

Turkish officials have not commented on the arrests.

Sabah said the initial hearings in the trial would last four days.