Upon hearing the news of Koslov's attack at Nummijärvi, Russian General Bibikov (positioned at Ömossa, south of Lappfjärd), likewise decided to attack, with 2,150 men of his own, thinking his numerical superiority could easily overwhelm the Swedish troops at Lappfjärd.

Unbeknownst to Bibikov, however, he would march against a Swedish force more than twice the size of his own, under Eberhard von Vegesack, who had landed at Kristinestad with 3,000 men, on 28 August, and taken command over the troops at Lappfjärd.

On 29 August the Russians launched a fruitless attack on the Swedes; attempts were made to force the Swedish flanks to give way, but in vain.

[3] At Lappfjärd the Swedish commander, von Vegesack, had greatly overestimated the Russian strength and thus failed to deliver a crushing defeat.

The Swedes were forced back with a loss of 64 killed or wounded, but not before several Russian attacks had been repulsed (among others, made by the Cossack Life Guards Regiment).