Japan started their WBSC Under-18 Men's Softball World Cup campaign in dominant fashion, thrashing New Zealand 12-1 ©WBSC

World number one Japan underlined their quality with a comfortable 12-1 win over hosts New Zealand in their opening World Baseball Softball Confederation (WBSC) Under-18 Men's Softball World Cup game at Colquhoun Park in Palmerston North.

Japan, who last won the tournament in 2016 and were runners-up in the last edition, scored five runs in the first inning to race into an early lead.

It was a sign of things to come and they had 12 runs on the board after three innings. 

Masaru Nishimori scored three runs for Japan and Hitto Nagayoshi drove in six, while the impressive Takuro Inagaki pitched 4 innings for 2 hits and one run with 6 strikeouts.

The final score was 12-1.

Elsewhere, Mexico recovered from a slow start to soundly defeat the United States 10-1 in an upset.

Pitcher Fernando Lopez allowed just one hit and one run over five innings. 

However, neither victory would be the biggest of the day; that feat goes to Guatemala - the tournament's lowest seed - who thrashed Denmark 16-1 in the opening match.

Further evidence that the World Cup could be won by anyone this year came from Singapore, who beat Argentina - the top seeds in Group A and two-times World Cup winners - in a shock 8-3 win.

In the other two matches, Australia started their title defence with a win, holding off a late rally from the Czech Republic to triumph 4-3, while Canada had no problem beating South Africa 6-1.