A diplomatic war of words between Switzerland and Russia has intensified, with the Swiss demanding that Moscow cease spying activities on its territory after two suspected espionage cases came to light in recent days.

"The Swiss Department Of Foreign Affairs has called on Russia to immediately end illegal activities on Swiss soil or against Swiss targets," it said on September 16.

The Swiss ministry said it summoned Sergei Garmonin, Moscow’s ambassador in Bern, to protest Russian activity in Switzerland.

The statement did not cite specifics, but it came a day after newspaper reports said Russian spies had allegedly targeted a laboratory in Spiez that was testing the nerve agent used on Russian double agent Sergei Skripal in the English city of Salisbury in March.

The lab also tests suspected weapons of the type allegedly used by Russia's ally, the Syrian government, in that country's civil war.

It is the third time the ministry has summoned the Russian ambassador this year to protest alleged attacks on organizations operating in Switzerland.

In the most recent case, the Swiss government on September 15 confirmed reports that Dutch authorities had arrested and expelled two suspected Russian spies earlier this year after the two allegedly tried to hack the Swiss laboratory.

Switzerland summoned the Russian ambassador to protest the “attempted attack” as Moscow rejected the allegations, the latest Western claim about Russian spying and other acts of interference.

The alleged target in the recent case was the Spiez Laboratory, which analyzed samples from the March poisoning of former Russian spy Sergei Skripal and his daughter in England.

Britain says Moscow used Novichok to try to kill Skripal and has charged two Russian men in absentia with attempted murder.

Skripal and his daughter Yulia recovered from the attack, but a British citizen, Dawn Sturgess, died in June and her boyfriend, Charlie Rowley, fell ill when they stumbled across remnants of the poison in a town near Salisbury.

Meanwhile, Swiss prosecutors revealed they were investigating a March 2017 cyberattack against the offices of the World Anti-Doping Agency (WADA) in Switzerland.

WADA, based in Montreal, suspended RUSADA, Russia's anti-doping agency, in 2015 over alleged state-backed doping in sports. Moscow has repeatedly denied state involvement in doping.

The individuals concerned in that probe were the same pair identified by the Swiss intelligence service a day earlier, prosecutors said.

The Russian Embassy described the newspaper's allegations as "unsubstantiated" and "baseless."

"This seems an absurd attempt to give readers a biased view of the Russians working in Switzerland," the Russian Embassy said.

With reporting by Reuters, BBC, and The Financial Times