Estonia is trying to make contact with an Estonian security official detained by Russia after a scuffle at the border.
Russia has refused to let the Estonian consul in Moscow meet Eston Kohver.
FSB, which is Russia’s domestic security service, claims it detained Kohver for carrying out a "spying operation" on Russian soil.
"We don't know where they are keeping him behind bars," the Estonian Security Police (Kapo) told the BBC Monday.
There is a dispute about whether Kohver was seized on Estonian or Russian soil.
The incident – which Estonia called the abduction of Kohver by "unidentified individuals from Russia" near the Luhamaa border checkpoint – forced the country to summon the Russian ambassador Friday.
During the seizure, the alleged abductors reportedly jammed Estonian radio communications and used a smoke grenade, according to the BBC.
"We had protection for him," police spokesman Harrys Puusepp said, but there were "explosions" during the incident which enabled the assailants to abduct Kohver at gunpoint.
The FSB claimed Kohver was caught carrying a gun, $6,539 in cash, an eavesdropping device, and "other materials related to intelligence-gathering."
Puusepp denied the claims and said Kohver "isn't in counter-intelligence - he was working on organized crime, contraband and corruption."
"We have proof he was definitely on Estonian ground. In that area the Estonian border is not fenced, it's bushes, high grass and forest. There's no line on the ground but everyone knows where it goes, it's recognized by both sides," Puusepp told the BBC.
"As far as we know he wasn't injured," he added.
Puusepp said the “consul needs to meet him and get to the bottom of this situation.”
Tension is already high in the region with the European Union and NATO accusing Russia of directly helping separatists in eastern Ukraine with regular troops and heavy weapons. Russia denies providing any assistance to the rebels.
Estonia -- like neighboring Baltic states Latvia and Lithuania-- joined NATO in 2004.
Puusepp said the border incident was "very unusual - I can't remember anything like this since Estonia regained independence [in 1991]".