ZURICH (Reuters) - Turkey’s ambassador to Switzerland has denied that his embassy spied on expatriate Turks, distancing his staff from a criminal investigation by Swiss prosecutors into suspected espionage.

The probe has drawn Switzerland into a dispute between Ankara and several European nations as Turkey seeks to drum up support in its diaspora in the run-up to a referendum on Sunday on expanding the powers of President Tayyip Erdogan.

“It is certain that no such activities were conducted within the realm of our embassy,” Ambassador Ilhan Saygili was quoted as telling broadcaster SRF’s Rundschau program in an interview to be aired on Wednesday night.

Saygili said that his deputy in Bern had been removed from office but did not confirm media reports that the diplomat and his family had sought asylum in neutral Switzerland.

“If he is absolutely not guilty then he could have gone to Turkey and proven his innocence,” the ambassador was quoted as saying, without specifying any accusation against his number two.

Embassy officials in Bern could not be reached immediately.

The Swiss foreign minister told his Turkish counterpart last month that Switzerland would “rigorously investigate” any illegal spying by Ankara on expatriate Turks before the referendum.

The Swiss investigation follows alleged intelligence gathering in which participants at events at the University of Zurich in late 2016 and early 2017 were filmed or photographed, according to Swiss media.

One of the reported instances was in December, where opposition Turkish newspaper Cumhuriyet’s chief editor was honored. The other was in January during an academic forum on mass killings of Armenians in Turkey 100 years ago that Armenians consider genocide, a term Ankara rejects.

Allegations of intelligence gathering by Erdogan supporters have arisen elsewhere in Europe. German police in February raided the flats of four imams suspected of spying for Turkey’s government on followers of U.S.-based cleric Fethullah Gulen, accused by Ankara of organizing a failed coup last July.

The head of Turkey’s Diyanet religious authority, Mehmet Gormez, has denied its imams engaged in illegal activities and called such allegations defamatory.

Swiss government statistics show 68,000 Turkish citizens live in Switzerland, while the Turkish embassy’s website puts the figure at 130,000.