NATO has no clear "red line" for invoking Article 5 – adviser to the President of Lithuania
Kyiv • UNN
NATO has not defined a clear threshold for Article 5 in response to Russian sabotage. It could be invoked after significant infrastructure damage or casualties.

It is difficult for NATO to determine the exact threshold at which Russia’s hybrid attacks and acts of sabotage could become grounds for invoking Article 5 on collective defense. This was stated by Lithuanian President’s chief adviser Dეividas Matulionis, LRT reports, as cited by UNN.
Details
According to Matulionis, the Alliance countries do not currently consider Russian acts of sabotage grounds for invoking Article 5; however, the situation could change in the event of serious damage to critical infrastructure or casualties.
Of course, this threshold is very unclear. I think that if critical infrastructure were seriously damaged, if there were casualties, the affected countries would request the activation of Article 5
Matulionis acknowledged that among the allies there are countries that are very cautious about the risk of further escalation. At the same time, he said that a direct Russian military invasion of the territory of a NATO country, even on a limited scale, would already constitute a situation for invoking Article 5.
The Lithuanian president’s adviser assessed the current threat of a direct military invasion as "almost zero," but stressed that the danger of Russian acts of sabotage and subversion remains and has intensified recently. In his view, Moscow is trying in this way to intimidate European societies and weaken support for Ukraine.