Vanuatu's Azariah Soromon celebrates his first goal in a 3-1 win over Papua New Guinea ©OFC

Defending champions and hosts Fiji and Vanuatu opened their Group B campaign at the Oceania Football Confederation (OFC) men’s Olympic qualifier with wins in Lautoka.

Fiji, seeking to follow qualification for Rio 2016 by booking a spot at Tokyo 2020, had to work hard for their 4-1 win at against a determined Tonga side at Churchill Park.

The game remained scoreless until the 55th minute, when the home side went ahead Patrick Joseph converted a disputed penalty.

Fiji captain Savenaca Baledrokadroka made it 2-0 with a brilliant effort on the hour and Joseph scored his second goal of the match six minutes later.

Substitute Bruce Hughes made it 4-0 in stoppage time before Hemaloto Polovili pulled a goal back.

"The first game is always tough to crack and I think Tonga gave us a hard time in the beginning," Fiji coach Marika Rodu said.

Vanuatu were ahead against Papua New Guinea after just three minutes when New Zealand-based Azariah Soromon headed home.

In the 19th minute Soromon added a second as he converted a penalty given after he had been fouled.

Moments later Bong Kalo set up Ronaldo Wilkins to make it 3-0.

Papua New Guinea pulled a goal back in the 52nd minute when their captain Gregory Togubai won and converted a penalty, but they could not earn any further material reward from the match.

The OFC Olympic qualifier resumes on Tuesday (September 24) with Group A matches in Suva and Group B matches continue on Wednesday (September 25) in Lautoka.

Only the winner of the tournament will qualify for Tokyo 2020.