"Crazy person stabs seven AP people while they were waiting for the President. Two have been killed," Mr Correa said in his Twitter account, referring to supporters of the ruling Alianza Pais political movement, known as AP.
In a video shown on local TV a man could be seen attacking pro-government supporters with a large knife.
The incident occurred on Monday ahead of a campaign rally in Quininde, a town in the western Esmeraldas province.
Mr Correa, 49, is expected to win the February 17 vote.