Russia has attempted to breach personal smartphones belonging to NATO troops as part of a campaign to gain information on operations, intimidate soldiers, and measure troop strength, according to a report.

Western military officials told the Wall Street Journal they believe Russia is behind the efforts to compromise smartphones belonging to NATO troops, officers, and government officials.

Russia's campaign specifically focused on the 4,000 NATO troops that were sent to Poland and the Baltic states, where they're protecting the border European member countries share with Russia.

U.S. Army Lt. Col. Christopher L'Heureux, commander of a NATO base in Poland, said cellphones or Facebook accounts belonging to at least six soldiers have been hacked, including his own.

In one instance, L'Heureux told the Wall Street Journal his personal iPhone had been hacked and reported lost. L'Heureux said the hacker had tried to compromise the phone through a Russian IP address.

An Apple map appeared on the phone, and in the center of it was Moscow, with a message stating "'Somebody is trying to access your iPhone,'" L'Heureux told the Wall Street Journal.

The U.S. Army lieutenant colonel also said he discovered he was being tracked through his smartphone.

In January, NATO soldiers at the Tapa Military Base, located near Estonia's border with Russia, also said "strange things" were happening with their cellphones, an officer told the Wall Street Journal.

The officer said an investigation into the incidents found Russia used a portable telephone antenna to breach the phones and erase information on them, including contacts stored on the phones.

In another instance in March, a phone belonging to an Estonian conscript began playing hip-hop music and contacts on the phone started disappearing. The conscript, stationed near the Russian border, hadn't downloaded the music that was playing.

According to the Wall Street Journal, Western military officials said the Russian campaign hasn't caused much damage, and much of the information is public.

Military cyber-espionage experts said Russia's actions indicate the country is trying to determine if there are more NATO troops stationed at new bases than disclosed.

Other Western officials warned hacked cellphones could lead to confusion among NATO troops.