Henrique Capriles said the alliance won at least 112 seats in Congress.

If confirmed, this would allow the opposition to make sweeping changes to legislation and appointments made under the current Socialist government.

President Nicolas Maduro earlier admitted defeat - the worst for the movement founded by late leader Hugo Chavez in 1999.

The National Electoral Council has already announced that the opposition won 99 seats in the 167-member assembly.

The Socialists have gained 46 seats, with another 22 yet to be declared.

At a later news conference, Mr Capriles said the opposition had a two-thirds majority, with four seats left to declare.