Just a small note of these often forgotten (and for a good reason, as they are minor) clashes. Following the start of the unsuccessful but massive Soviet air offensive on Finland on 25th of June 1941 the Finnish military decided upon its own preparations. On 28th of June Finnish command issued an order about preparations for the advance to the main force or the army and gave permission to the units to start reconnaissance beyond the border. However major engagements and pushing through the defenses was not permitted as troops waited for the go-ahead of the main offensive which started later on (on July 9th).
Fighting at Enso (Svetogorsk) - 29th of June - https://www.google.com/maps/@61.1155069,28.8211386,10274m/data=!3m1!1e3 . Finnish scouts investigates on 29th June the factory town of Enso located right at the border (on the Soviet side). They found the town to be undefended. On his own initiative the division commander of the Finnish 18th Division ordered the light detachment (battalion) to capture it. However between the scouts reports and the arrival of the actual troops the Soviets had also sent troops to the town. Which lead to a more or less of a meeting engagement and the following battle continued for some time.
What made this peculiar engagement is that the Finnish troops couldn’t get much support as the commander of the Finnish II Corps forbade sending additional troops or use of artillery. During the fighting the Soviets used tanks in a counter attack which pushed the Finns back to the border at which point the Finnish artillery was committed which in turn pushed the Soviets back from the border. The town of Enso remained in the Soviet hands. It is worth noting that while this might sound impressive… the center of Enso is just 2 km from the border so the ‘advance’ was in really small scale.
Fighting at Tyrjä - 30th of June - https://www.google.com/maps/@61.5330217,29.6379623,14337m/data=!3m1!1e3 . The Finnish rules of engagements were changed due to the clash that happened at Enso. The Finnish 2nd Division chose to advance in force to capture the undefended terrain in front of them before the Soviet defense lines. In the end the Finnish 2nd Division had captured roughly 10 km wide and 10 km deep wedge and held it against the Soviet counterattacks. This wedge reached fairly close (roughly 10 km) to the main railroad link north of the Lake Ladoga.
[Personal opinion: after looking at the maps it seems that ‘10 km deep’ is a gross exaggeration, reality seems to be somewhere closer to 5, which i guess can be rounded up to 10…]
Fighting at Värtsilä - 6th of July - (https://www.google.com/maps/@62.1772948,30.667182,16696m/data=!3m1!1e3).
Finnish 11th Division was instructed to push forward until strong resistance was encountered. The advance easily overran the first Soviet defenses but encountered strong resistance which together with the difficult (roadless) terrain caused the advance to be bogged down. Fighting continued all the way to the start of the main offensive.
Fighting at Ilomantsi - 7th of July - ( https://www.google.com/maps/@62.62749,31.2849823,27660m/data=!3m1!1e3 ).
On 7th of July the roughly division sized Group O or Group Oinonen (named after its commander as was tradition in the Finnish military) started its advance. This force was to advance capturing more advantageous terrain before the main offensive however without getting entangled into major fighting. Soviet defenses were met already on the same evening and the advance was halted.
Outside of the main body of troops one other Finnish forces also started action. On 4th of July the Finnish 14th Division (directly under the command of the Finnish GHQ) started its advance towards Rukajärvi (Rugozero - https://www.google.com/maps/@64.0664913,32.7654907,18603m/data=!3m1!1e3 ) via Repola ( https://www.google.com/maps/@63.8431785,30.824702,15769m/data=!3m1!1e3 ). The start of that advance later inspired the movie Fin. ‘Rukajärven tie’ - Eng. ‘Ambush’ - Lit. ‘Road of Rukajärvi’ (1999) which loosely followed the actual events.