SYDNEY, Australia — More than a week after one of the closest and longest Australian national elections in half a century, Prime Minister Malcolm Turnbull declared victory on Sunday after the leader of the opposition Labor Party conceded defeat.

“We have won the election,” Mr. Turnbull, the leader of the Liberal Party-led conservative coalition, said at a news conference on Sunday.

The Australian Electoral Commission has forecast that the coalition could win a combined 76 seats, which would give it an absolute majority in the 150-seat House of Representatives. Two independent members of the House have also pledged their support to the coalition, solidifying its chances of forming a government.

“It is clear Mr. Turnbull and his coalition will form a government,” Bill Shorten, the Labor Party leader, said at a news conference on Sunday afternoon. “I hope they run a good government.”