Spanish Prime Minister Mariano Rajoy will meet the Socialist Party leader later Wednesday to begin negotiations on forming a new government following elections, his office said.

"Mariano Rajoy and Pedro Sanchez will meet at 12 pm (1100 GMT)... for the first time since the general elections", it said in a statement.

Rajoy's incumbent conservative party won the most seats in Sunday's polls, followed by the Socialists, but failed to secure an absolute majority.