World number one Mark Selby defeated Anthony Hamilton 4-1 in the first round of the Northern Ireland Open at the Waterfront Hall.
Selby hit a top break of 122 as he joined Ronnie O'Sullivan in round two.
O'Sullivan notched up three straight century breaks as he beat Soheil Vahedi 4-0 in under 45 minutes.
Belfast's Joe Swail has progressed thanks to a 4-1 win over Luke Simmonds, while Peter Ebdon coasted past home player Patrick Wallace 4-0.
Marco Fu, Hong Kong's world number 16, was surprisingly knocked out, beaten 4-2 by China's Chen Feilong, ranked 126th.
Scotland's Alan McManus defeated Allan Taylor 4-0 and Thai Thepchaiya Un-Nooh eased past Robert Milkins by the same scoreline, as did Jack Lisowski in his comfortable victory over Hossein Vafaei of Iran.
However, Irishman Ken Doherty and Englishmen Shaun Murphy, the world number 10, suffered first-round defeats. Doherty was beaten by Scott Donaldson and Murphy by Sam Baird.
In Tuesday's early matches, England's Andrew Higginson was handed a walkover against China's Liang Wenbo, while David Gilbert beat Irishman Fergal O'Brien 4-1.
Mark King, Robbie Williams, Scotland's Chris Totten, Lu Ning of China and Welshman Kishan Hirani were also among those to progress.