Seven Thai political parties led by one ousted from power in a military coup say they believe they have won enough seats to form the next government.

The announcement came amid concerns about potential irregularities in Sunday's vote, and before a full preliminary vote count has even been released. Official results aren't due until May.

The leader of the Pheu Thai party, which headed the government toppled in a 2014 coup, and the leaders of five other parties said Wednesday that they believed they had won more than 250 seats in the 500-seat lower house. They said another smaller had also agreed to join their potential government.

The ruling junta-backed Palang Pracharath party has also said it should form the government after appearing to have won the most votes.