Estonia's Police and Border Guard Board (PPA) said on May 23 that Russian border guards removed the boundary markers from the Narva River that separate Russian and Estonian territory.
The incident follows a Russian decree suggesting that Russian maritime borders in the Baltic Sea be unilaterally changed. The decree was subsequently removed from the government's website without an explanation following swift condemnation from some NATO members.
Eerik Purgel, head of the PPA's Eastern Prefecture, said that Estonian and Russian authorities install the buoys that separate the territories on a yearly basis in order to ease navigation on the river and prevent fishermen and others from accidentally straying across the border.
The respective authorities agreed on the buoys' location in 2022, but Russia then backtracked and disputed the placement of more than half of the 250 markers.
Russian border guards then unilaterally began removing them on May 23 without providing an explanation for their actions.
"The PPA will contact the Russian Border Guard and request clarifications on the removal of the buoys and return of buoys," Purgel said.
"The PPA expects evidence from Russia that the position of the shipping route agreed so far has changed and, if they are not presented, we will continue to install buoys."
Prime Minister Kaja Kallas characterized it as a "border incident" and said it was being investigated.
"We will approach this case in a sober, balanced way, engaging with allies where necessary. We see a broader pattern of Russian actions trying to sow anxiety," Kallas said.
Estonia began nightly closures of the crossing between Narva and the Russian border city of Ivangorod earlier in May.