Bantamweight John Joe Nevin and middleweight Darren O'Neill have both advanced to the last 16 in their Olympic boxing divisions.

Nevin advanced to the last 16 after comprehensively outpointing Denmark's Denis Ceylan in this afternoon's first-round bout.

Nevin landed early blows to take the fight to Ceylan from the outset and he finished the opening round with a 5-2 lead.

Controling the pace all the way through the second round, he picked off his opponent at will, racking up eight more points to just two for the Dane.

It was much of the same in round three as Nevin outfoxed and outclassed Ceylan, scoring another 8-2 victory for the round and a huge 21-6 total.

Nevin will face Kanat Abutalipov of Kazakhstan in the round of 16.

O'Neill made light work of Nigeria's Mudeen Akanji to advance.

In a tight first round, O'Neill edged it 4-3, with his superior tactics and punching power lending him the lead.

The second round was all O'Neill as he raced into a 12-5 lead. Strong lefts and combination punches gave him the scores with the tall Nigerian simply having no answer.

With the fight done, the last round become a matter of winding down the clock, which O'Neill did expertly, while also managing to outpoint his opponent 3-1. A final score of 15-6 in O'Neill's favour was merited.

Both fighters march on.

Adam Nolan is the next Irish boxer in the ring. He fights in Sunday night's evening session, which begins at 8.30pm.

Californian teenager Joseph Diaz Jr booked a last 16 bout against Cuba's reigning world champion Lazaro Alvarez Estrada with a slick performance in his bantamweight preliminary bout.

The 19-year-old Diaz pulled away from his rugged opponent Pavlo Ishchenko of the Ukraine, landing uppercuts and straight right hands in the final round as he skated to an impressive 19-9 victory.

Also at bantamweight, Australian teenager Ibrahim Balla survived an all-action showdown against Morocco's Aboubakr Lbida, crucially taking the final round to claim victory on countback after a 16-16 draw.

Former world champion Detelin Dalakliev of Bulgaria easily beat South Africa's Ayabonga Sonjica 15-6 while Italy's Jayn Parrinello will be Luke Campbell's first opponent after Parrinello beat Namibia's Jonas Matheus 18-7.

But there was heartbreak for 17-year-old Londoner Isaac Dogboe, representing Ghana, who took a two-point lead into the last round against Japan's Satoshi Shimizu but ended up on the wrong end of a contentious 10-9 verdict.

At middleweight, American Terrell Gausha staged a spectacular fightback against Armenia's Andranik Hakobyan, flooring his opponent twice in the final 10 seconds to force a stoppage with literally no seconds left on the clock.

In a wild, swinging contest, Hakobyan got the better of the first two rounds to lead by a point heading into the third. A huge overhand right decked the Armenian and a big follow-up shot gave Gausha the dramatic victory.

Uzbekistan's powerful former two-time world champion Abbos Atoev beat Badr-Eddine Haddioui of Morocco 11-9, while Azerbaijan's Soltan Migitinov looked a possible contender in defeating Egypt's Mohamed Hikal 20-12.

Cheered by a sizeable contingent of his compatriots, Indian superstar Vijender nudged into the last 16 at the expense of Kazakhstan's Danabek Suzhanov, extending his lead throughout to take a 14-10 verdict.