Australia recorded a six-wicket win over Ireland while South Africa, India and New Zealand also posted wins at the ICC U19 Cricket World Cup in Queensland on Tuesday.
The host nation took on Ireland at Endeavour Park in Townsville and produced a terrific bowling performance to dismiss their opponents for just 129 in the 43rd over.
Ireland did make a bright start though, reaching 32-0 from the first five overs as opener Ryan Hunter (31) got after the bowlers.
But the Irish collapsed from there, with medium-pacer Alex Gregory (3-13 off eight overs) and spinner Shane Cassel (3-24 off 10) the best of the bowlers for Australia.
Ireland had their tails up when Australia slumped to 45-3 in response, but captain Will Bosisto (36 not out), Sam Hain (26 not out) and Travis Head (25) all scored crucial runs as they claimed a six-wicket victory.
South African openers Quinton de Kock (126) and Chad Bowes (115) starred as they thumped Namibia by 209 runs in Brisbane.
De Kock – who scored 95 in South Africa's tournament opener against Bangladesh on Sunday – smashed 13 fours and three sixes in his superb innings.
Bowes also found the boundary with ease as the pair added 212 runs for the first wicket, with South Africa finishing on 359-6 from their 50 overs.
In response, Namibia were skittled for just 150 with Theunis de Bruyn (4-20 off five) cleaning up the tail.
Wicketkeeper De Kock took four catches, while Prenelan Subrayen (2-40 off 10) also bowled well.
Kamal Passi (6-23 off 8.1) led India to a 64-run win against Zimbabwe at Tony Ireland Stadium in Townsville.
India batted first and posted a total of 261-6 from their 50 overs, with Unmukt Chand scoring a terrific 78 from 85 deliveries.
Passi also chipped in with the bat, hitting three late sixes in his five-ball 24, before he ripped through the Zimbabwean top order.
And although Malcolm Lake (118) played a superb lone hand for the losers, they were bowled out for 198 in the 45th over.
The day's other match saw Afghanistan go close to pulling off an upset against New Zealand on the Sunshine Coast.
The Kiwis were bowled out for 198 after exactly 50 overs of batting, with Robert O'Donnell (69) and Henry Walsh (52) leading the way with the bat.
And after Afghanistan slumped from 19-0 to 26-5, the match looked as good as over.
Fighting efforts from Najibullah Zadrean (69) and Afsar Khan (42) saw the Afghans finish at 190-9 from their 50 overs though, as they fell just eight runs short.
Jacob Duffy (4-40 off 10) and Matthew Quinn (4-26 off nine) were the best bowlers for New Zealand.