Russian spying in Switzerland is increasing, the Swiss intelligence agency said on Friday after two high-profile cases involving suspected Russian agents trying to infiltrate sites in Switzerland.

“I cannot give a lot of details about the Russian activities in Switzerland but it is clear we have more activities than before,” Jean-Philippe Gaudin, director of the NDB intelligence service, told Reuters. “I cannot say how many spies, but it is significant.”

Swiss authorities believe two Russian spies targeted a Swiss chemical weapons testing facility and prosecutors are also investigating a cyber attack against the offices of the World Anti-Doping Agency in Switzerland.

Gaudin said Switzerland was being targeted because it hosts many international organizations and NGOs, particularly around Geneva. Sporting organizations like the International Olympic Committee could also be targeted.

He said spying did not just involve Russians, but also agents from other countries.

“What is different today is the Russians tried to act against our sensitive infrastructure, that is a red line,” he said.

The NDB said in September it had worked with British and Dutch counterparts to foil a Russian plot which, according to newspaper reports, was targeting a Swiss laboratory testing nerve agents such as Novichok. Britain says Moscow used Novichok to try to kill former Russian spy Sergei Skripal in the English city of Salisbury in March and has charged two Russian men in absentia with attempted murder.

The Russian embassy in Bern has dismissed the Swiss account as “absurd.”