Lithuania, which is on NATO's eastern flank, and fellow Baltic states Latvia and Estonia -- all bordering Russia -- fear they could be next in Moscow's crosshairs were it to win its war against Ukraine.

All three countries have been ramping up defences since Russia's invasion of Ukraine in 2022 and boosted border security over what they allege was a Russia-inspired influx of migrants at the border.

The latest spending push would allow Lithuania to "block and slow down the actions of hostile states", the defence ministry said.

It added that Lithuania would "allocate approximately 1.1 billion euros to the countermobility project over the next 10 years".

In January, Lithuania announced plans to spend an annual five to six percent of its GDP on defence from 2026 to 2030.

The defence ministry said "intensive" work was ongoing to identify how to "ensure the integrity of the Baltic defensive line".

It said 800 million euros of the overall sum would be spent on anti-tank mines.

The Baltic states also joined Finland and Poland in deciding this year to leave the Ottawa Convention that bans acquiring, producing, stockpiling or using anti-personnel mines.

The mines, designed to be buried or hidden on the ground, often mutilate victims, who do not immediately die, and aid groups denounce their long-term impact on civilians.

Human rights groups, including Amnesty International and the International Committee of the Red Cross (ICRC), have condemned the decision to abandon the treaty.

As part of the planned measures, Lithuania will stockpile weapons like anti-tank systems and harden defences near the so-called Suwalki Gap -- a strategically important area where Lithuania borders Poland.

The stretch of land is flanked by the Russian exclave of Kaliningrad on one side and by Moscow's ally Belarus on the other.

Military strategists say it is the Achilles' heel of NATO's eastern flank since its capture would cut off the alliance's three Baltic members.

Lithuania plans to deepen irrigation ditches that could serve as trenches, reforest border areas and plant trees on key roads to protect civilians and the military.

Additional measures include "electronic warfare capabilities, anti-drone systems and the strengthening of the observation and early warning system", the ministry said.