Beijing, Aug 22 (IANS): Defending champion Usain Bolt and his American rival Justin Gatlin dominated their respective heats to enter the men's 100 metres semi-finals at the World Athletics Championships here on Saturday.

Gatlin registered a time of 9.83 seconds, while Bolt kicked-off his title defence by clocking 9.96 seconds on the opening day of the biennial extravaganza at the Bird's Nest Stadium.

while Gatlin's show was the fastest on the day, two-time world champion Bolt's effort in the seventh heat was the fifth fastest. American Trayvon Bromell (9.91 seconds), Jimmy Vicaut (9.92 seconds) of France and fellow Jamaican Asafa Powell (9.95 seconds) were better on the day than the two-time Olympic champion.

Apart from these five, Chinese Bingtian Su (10.03 seconds), South Africa's Akani Simbine (10.09 seconds), Nickel Ashmeade (10.19 seconds), Frenchman Christophe Lemaitre (10.24 seconds), Ramon Gittens (10.02 seconds), Ben Youssef Maite (10.05 seconds), Richard Kilty (10.12 seconds), Chijindu Ujah (10.05 seconds), Julian Reus (10.14 seconds), Andre De Grasse (9.99 seconds), Jak Ali Harvey (10.04 seconds), Aaron Brown (10.03 seconds), Henricho Bruintjies (10.07 seconds), Hassan Taftian (10.10 seconds), Mike Rodgers (9.97 seconds), Churandy Martina (10.06 seconds) and Levi Cadogan (10.12 seconds), Femi Ogunode (9.99 seconds) and Tyson Gay (10.11 seconds) will compete in Sunday's three semi-finals.