MOSCOW, Feb 10, 2015 (AFP) - What do a nuclear scientist, a young mother of seven, a church employee and a former military factory boss have in common?

They've all been charged with high treason, espionage or disclosing state secrets in newly spy-phobic Russia.

With ex-KGB President Vladimir Putin staking his reputation on Russia's takeover of Crimea and the success of pro-Moscow separatist fighters in eastern Ukraine, Russia is seeing "an upsurge of spy mania," prominent lawyer Anna Stavitskaya said.

The start of the Ukraine crisis more than a year ago has coincided with a ramping up of Kremlin efforts to squelch dissent by further sideling opponents and muzzling what's left of Russia's independent media.

But the speed and sweeping nature of the crackdown, based on new legislation, has been surprising, lawyers and activists say.

Stavitskaya represented arms control expert Igor Sutyagin, who was sentenced in 2004 to 15 years in jail over handing classified information to a British company, although he says the information was available in the public sphere.

She remembers the first wave of "spy mania" when the security service targeted scientists in the late 1990s.

Today, she says, the FSB security service, successor to the feared KGB, appears to be casting a much wider net.

"The entire spectrum of Russian civil society" has been targeted with treason accusations, Stavitskaya said.

The state's message, she added, is: "Everyone needs to think seriously about what to say and where."

After Putin returned to the Kremlin for a third term in 2012, Russia broadened its definition of treason and espionage, alarming rights groups that said nearly anyone could fall afoul of the new law.

The wording of the amended legislation is so vague that nearly anyone - including those without access to state secrets - can now be accused of a grave crime against the state, experts warned.

"Once an investigator moves to use his imagination, any contact with a foreigner can be deemed high treason," Ivan Pavlov told The New Times opposition magazine.

Pavlov represents the interests of mother of seven Svetlana Davydova, who has become a cause celebre for the country's embattled civil society.

Her arrest last month for allegedly calling the Ukrainian embassy with information on Russian troops movements stunned a country where many have become inured to injustice. Davydova maintains that she was not spying, saying she is just a housewife with no access to state secrets, but had become worried that troops from her town were apparently being sent to Ukraine - where Russia claims it is not fighting.

After tens of thousands signed a petition calling on Putin to release the young mother, Davydova last week walked out of the high-security Lefortovo prison but the charges against her remain in place.

It emerged soon after that several more Russians - and Ukrainians - have been arrested on similar charges over the past year and face up to 20 years in prison.

The list of people caught up in the spy net could have come from the chronicles of Soviet-era repression.

Nuclear scientist Vladimir Golubev was arrested last summer on charges of disclosing state secrets after publishing an article in a Czech journal.

Yevgeny Petrin, a former employee of both the Moscow Patriarchate in Kiev and before that the security service, was detained on charges of treason last June.

Yury Soloshenko, the elderly former director of a military factory in Ukraine, was arrested on charges of espionage last August.

The list goes on and on, said prominent rights activist Zoya Svetova.

She said that it was impossible to know just how many Russian and foreign citizens exactly are being held in the Lefortovo jail overseen by the FSB security service and other prisons.

But one thing links "all high-profile treason cases," she said: Ukraine.

Intelligence expert Andrei Soldatov ruled out a return to the industrial-scale repression seen in the Soviet Union, but said authorities may well resort to "show trials of the 1930s" to keep the opposition in check and channel aggression in society.

"The crisis is deepening, the Kremlin is growing increasingly jittery and no one knows how this will all end," he said.

Popular blogger and literary critic Nikolai Podosokorsky said Russians would likely learn of more treason cases in the near future.

"It looks like a campaign to whip up fear and suspicions in society is only beginning to gain momentum," he wrote in his blog.