Spain appears destined for painful political negotiations after Sunday's elections, when no single party won enough parliamentary seats to form a government. Prospects for coalition-building now remain uncertain.

With 97% of the vote counted, the center-right Partido Popular (PP) is set to win 136 seats, and the far-right Vox party is forecast to win 33.

The ruling center-left Socialist party meanwhile is on course to win 122 seats, with likely coalition partners Sumar on 31 seats.

In order to govern, a party or coalition must achieve a working majority of 176 seats in the 350-seat legislature.

There are also a number of smaller regional parties set to win seats. Several of them lent support to Prime Minister Pedro Sanchez's coalition government prior to this election, and it is unlikely they would join forces with the rightwing PP and Vox.

Calling Sunday's vote was a political gamble for Prime Minister Pedro Sanchez, after his Socialist party suffered major setbacks in regional and local elections in May.

The PP that month made huge gains, amid a surge toward the right in European politics across the continent. But Sunday's nailbiting vote count has offered no easy path for a rightwing coalition to be formed.