Tirana says it is cautious to talk about the motive of the intruders but indicated geopolitical developments.
Albania has said it was investigating why two Russians and a Ukrainian had tried to enter a military factory as police detained four Czech nationals also close to another military plant.
The defence ministry said late on Saturday that two of its soldiers were slightly injured while detaining a 24-year-old man from Russia who had entered the grounds of the Gramsh military factory and was trying to take photos. He resisted arrest and used spray against the soldiers.
Two others –– a 33-year-old Russian woman and a Ukrainian man aged 25 –– were arrested nearby.
Defence Minister Niko Peleshi said on Sunday that it was too early to be sure about the motive but hinted at a possible link to Russia's attack on Ukraine, which has been criticised by Albania.
"In view of the broad regional context and the geopolitical context, this cannot be dismissed as just as an ordinary, civilian incident, but we cannot rush to conclusions," he said after visiting the injured soldiers in hospital.
Albanian Prime Minister Edi Rama said on Saturday the three individuals were "suspected of espionage" without giving further details.
Tirana-based media said the three suspects were bloggers who often visited abandoned military bases and other big plants in different countries.
Peleshi said the investigation would show if they were bloggers and speak to their motives.
Czech nationals detained
When Albania was under communist rule, the Gramsh plant produced Russian-designed AK 47 rifles.
The ministry's website says the plant now provides manufacturing services for the defence industry. In the past, it was also used to dismantle small arms and ammunition.
In a similar incident police said on Sunday four Czech nationals had been detained at the Polican military plant.
Police said two Czech women were initially spotted outside the plant and two other men were found inside the tunnels.
Tirana media reported all four said they were tourists.
The Polican plant was used during communism to produce ammunition for Russian made rifle AK 47, hand grenades, anti-personnel and anti-tank mines. Some foreign tourists who have visited the place previously have managed to enter the tunnels where the ammunition was made, and they have published their photos on internet.
From their photos the area looked abandoned where old machines and bullet rounds are seen on the ground.
Albania, a member of NATO since 2009, has joined the United States and other western countries to condemn Russia's attacks on Ukraine and has introduced sanctions against Moscow.