Poland is boosting its defensive capabilities amid increasing concerns that the conflict in Ukraine could spill over the border. The NATO member country has been facilitating the passage of western arms bound for Ukraine, convoys that Russia has warned could be viewed as legitimate military targets.

This makes Janusz Lech very nervous. He owns rental chalets in the small town of Dubiecko in eastern Poland.

"The convoys take the main road here from Przemyśl to Rzeszów," Lech told CGTN. "There may be some attempts by Putin. Some convoys might be bombed... because there's a military base very close to here."

"We have bags packed in case we need to leave quickly," his wife added in whispered tones.

Poland has been put on high alert after airstrikes killed 35 at the Yavoriv military base in Ukraine, where NATO troops were known to have trained Ukrainian forces.

This was Russia's most westward attack, just 20 kilometers from the Polish border.

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Security analyst Michał Piekarski from the University of Wrocław believes this is a direct message from Russia to the West.

"They (Moscow) are clearly trying to say 'we have superweapons, we have long hands and we can strike close to the border, our missiles can cross the border,'" he said. "Russia wants people to doubt NATO's defense capabilities."

Residents in the eastern Polish city of Lublin, are also concerned.

At the moment, yes, we are very afraid," admitted Elzbieta, "because we are really close to the border and you never know what will happen with this bad man (Putin). We are really afraid."

So far NATO has refrained from any action that might place it in direct confrontation with Russia but it is supporting Ukraine with military equipment.

It is also beefing up its members that are the closest to the conflict, such as Poland, with more troops, weapons and air patrols.

Warsaw has also introduced the "Homeland Defence Act", which increases defense spending to 3 percent of GDP, and more than double the size of its armed forces.

Deputy Prime Minister Jarosław Kaczynski applauded the support of Poland's NATO allies, but said that the country must also defend itself against potential Russian "imperial ambitions."

"We think that it is a good idea," say lifelong Lublin residents Barbara and Kazimierz. "A safe country should have a good military, especially while Russia is such a possessive country that doesn't' follow democracy."

Sharing a 500-kilometer border with Ukraine, across which weapons go in and refugee come out, exposes Poland to potential Russian revenge. But some do find comfort in NATO, says Piekarski.

"People are concerned, people are worried, but personally, I feel safe. I feel safe that NATO is here."

But an attack on one NATO member is considered an attack on all members, meaning that if Russia, a nuclear power, does decide to strike over the border, it could inflame the conflict to unpredictable levels.