 Molotov claimed that it was a Finnish artillery attack and demanded that Finland apologise for the incident and move its forces beyond a line 20 – 25 km ( 12 – 16 mi ) away from the border . Finland denied responsibility for the attack , rejected the demands , and called for a joint Finnish – Soviet commission to examine the incident . The Soviet Union then claimed that the Finnish response was hostile , renounced the non @-@ aggression pact and severed diplomatic relations with Finland on 28 November . In the following years , Soviet historiography described the incident as a Finnish provocation . Doubt on the official Soviet version was cast only in the late 1980s , in the times of glasnost . However , the issue continued to divide Russian historiography even after the collapse of the Soviet Union . 
