The Baltic states are stepping up coordinated efforts to identify people among their populations who have been recruited by Russian intelligence agencies, say officials.

Security chiefs in Estonia, Latvia and Lithuania fear the Kremlin has increased recruitment not only of "assets" tasked with engaging in the classic spying activity of gathering sensitive information, but also possibly to lay the groundwork for sabotage and subversion and to assist in so-called "Russian influence activities," according to Baltic officials.

And all three countries are scrambling to better prepare for hybrid warfare, in case their giant neighbor decides to launch the kind of hybrid destabilization campaign it has waged since 2014 in Ukraine. Later this year, a special fusion cell will become operational with U.S. help.

Latvian central bank sign is seen on the bank's headquarters in Riga, April 9, 2019.

On Thursday, Latvian banks participated in an exercise simulating a Russian-fomented crisis to test their resilience.

"The financial sector's ability to work during hybrid warfare is an essential part of the comprehensive national defense system," said Latvian Defense Minister Artis Pabriks. He added, "For that reason, we organize such exercises with banks and other leading institutions of this sector."

The resilience tests of the banks, aimed at trying to ensure they are able to withstand hacking and sabotage, came as Russia concluded a massive naval exercise, dubbed Ocean Shield, in the Baltic Sea. The exercise, which ran from Aug. 1 to 9, involved 49 warships, 20 support vessels and more than 10,000 military personnel, and was larger than a maritime drill last year in the Mediterranean Sea, say Western defense experts.

According to Estonia's Foreign Intelligence Service, Russian spies and their agents have been caught in operations in greater numbers than usual since 2014 in the Baltic states. Their proximity to Russia, the legacy of their Soviet pasts as well as hosting substantial ethnic Russian communities make the Baltic states especially vulnerable for Kremlin intelligence activities, say analysts.

All three Baltic states were among the first of 15 Soviet republics to declare independence. They joined the European Union and NATO in 2004.

Latvia, Lithuania and Estonia

In a report earlier this year, the Estonian intelligence agency warned that a clash with Russia could be triggered by a pro-Western tilt in nearby Belarus. All three Baltic states have pursued a series of high-profile spy cases in recent months.

In January, a court in Vilnius, Lithuania's capital, convicted 67 Russian, Belarusian and Ukrainian citizens on spying charges, sentencing them to prison terms ranging from four to 14 years. The charges stemmed from the defendants' activities in 1991, when Russia tried to halt the Lithuanian move toward independence. The convictions prompted an angry reaction from the Kremlin.

In July 2017, another court in Vilnius sentenced a Russian security official, Nikolai Filipchenko, to a decade in prison after finding him guilty of attempting to recruit local officials to wiretap the home of Lithuania's president. And in April, a Lithuanian court sentenced a Russian-born sailor to seven years in prison on charges of spying for Moscow, the latest in a series of espionage-related cases between the two countries. He supplied classified information about port infrastructure.

And the country's authorities are still pursuing an espionage case against leftist lawmaker Algirdas Paleckis, the scion of one of Lithuania's most famous political dynasties. Paleckis, the leader of the Socialist People's Front, a fringe left-wing party he founded after leaving the larger Social Democratic party, opposes Lithuania's NATO membership.

Exactly what espionage Paleckis is alleged to have conducted hadn't been fully revealed. But Marius Laurinavicius, an analyst with the Vilnius Institute of Policy Analysis, a research group, believes "it involves a ring of agents of Russian influence."

A woman leaves Estonia's central bank in Tallinn, Estonia, March 25, 2019.

A court in Estonia in February found a former Estonian military officer and his father guilty of treason for spying and for handing Estonian and NATO secrets to Russia. The court in Tallinn ruled that 38-year-old Deniss Metsavas — a former major with the Estonian army — and his 65-year-old father sold classified information to Russia's military intelligence service, the GRU.

Metsavas, who received a 15-year prison term, had supplied information for a decade to the GRU. In an interview in June with The Atlantic, an American magazine, he said he was first approached by Russian recruiters while on a visit to his Russian relatives in 2007.

At a nightclub in Smolensk, he met an attractive woman and spent a night with her. Later, two men dressed in plain clothes approached him and said they were police officers and showed him an affidavit in which the woman claimed he'd raped her. He was released and allowed to return to Estonia but blackmailed into cooperating with the GRU, he said.

Most espionage cases in the Baltic states involve Russian agents trying to gather information on military infrastructure, troop movements and energy supply grids as well as missions involving efforts to wiretap officials and politicians. In Latvia, which has amended criminal laws to assist in prosecuting intelligence cases, a national firearms system manager was arrested earlier this year on espionage charges.

Latvia has also prosecuted a man caught gathering information about an army base, petroleum product warehouses and border posts, and a railway worker, Aleksandrs Krasnopjorovs, who supplied footage to Russia from a video surveillance system of NATO military movements. He is appealing his conviction.