Serbia began their title defence in impressive fashion ©Getty Images

Olympic gold medallists Serbia and reigning world champions Croatia eased to victories in their opening matches of the preliminary rounds of the men's European Water Polo World League.

Reigning World League champions Serbia brushed aside the challenge of Romania in their home match in the city of Zrenjanin.

The hosts eased into a 6-1 lead by half-time in the contest, which made the result seem inevitable.

Serbia were able to celebrate the victory by outscoring their opponents in the final two quarters, despite some Romanian resistance, to win 12-3.

The result places them at the top of the Group A standings, with their next clash due to come against neighbours Montenegro.

Croatia, who claimed the world title earlier this year, impressed throughout their match against Russia in Zadac.

They cruised to a straightforward 14-4 win over the Russian squad, although their opponents will take the positives of scoring in three of the quarters against the world champions.

The final group match of the first round of fixtures saw Spain secure victory in front of a home crowd in Malaga.

World champions Croatia won their opening preliminary match ©Getty Images
World champions Croatia won their opening preliminary match ©Getty Images

Spain moved into a 5-2 lead over The Netherlands by half-time, before the Dutch squad outscored them 2-1 in the third quarter to close the gap.

They proved unable to complete a comeback as Spain regained the momentum to seal a 9-5 win in Group C.

Both Croatia and Spain will rest during the second round of preliminary matches on December 12, with Germany set to face Russia in Group C.

World Championship silver medallists Hungary will play their opening Group C fixture against The Netherlands.

After the conclusion of six rounds, the four best teams will be qualified for the Super Final.

It will be  held from June 18 to 23, with the European teams set to be joined by four other sides who have qualified from Intercontinental Tournaments.