WARSAW (Reuters) - Several Polish municipalities that have hosted U.S. troops under a planned NATO operation suffered cyber attacks in January, a senior government official told Reuters, saying it highlighted the need for Poland’s sharp increase in cyber-defense spending.

Poland will spend about 1 billion zlotys ($250 million) a year on cyber security, several times the amount seen only a few years ago, following a trend in other NATO countries that have been increasingly subject to Internet security breaches.

“We are constantly seeing large destructive cyber and information activity by certain countries,” Deputy Defense Minister Tomasz Szatkowski said in an interview. “The process has been intensifying.”

He declined to specify who was behind the attacks, but said they included pro-Russian content.

The websites attacked with anti-NATO and anti-U.S. propaganda in January belonged to at least two municipalities where thousands of U.S. troops along with tanks and heavy equipment arrived to beef up NATO’s Eastern European allies.

“It is clear to us who is the author and who inspires such activities,” Szatkowski said. The attacks aimed at sowing a negative image of Poland’s allies and “presenting the Russian version of the conflict in eastern Ukraine”, he said.

The largest U.S. military reinforcement of Europe in decades of about 2,700 troops, out of 3,500 planned, arrived in mid-January as part of operation Atlantic Resolve, aimed at showing Moscow Washington’s commitment to its allies.

The Kremlin said the troops’ presence is a threat to Russia.

Higher spending on cyber security is one of the top priorities for the ministry over the next five years, along with enhancing Poland’s armed forces, air and sea patrols as well as the formation of a territorial defense forces.

Modernization of the army has been a key priority for the government run by the conservative Law and Justice (PiS) party, which built its popularity partly on promising greater security and deterrence against cross-border threats from Russia.

Poland spends about 2 percent of its gross domestic product on defense, although some military officials press for more, saying that nearly two-thirds of the armory dates from the era when the country was in the Moscow-led Warsaw Pact.

Warsaw is awaiting a U.S. government export approval to close a $5 billion deal to buy eight Patriot missile defense systems from Raytheon Co, a purchase considered central to the modernization plans and Poland’s strategy towards Washington.

“The United States is our key ally,” Szatkowski said. “Opinions that we should take into account only the armament and military equipment produced in Europe, are not correct.”