Two-time Olympic Games champions Netherlands staged a late rally to beat Belgium 3-1, but they were indebted to penalty corner striker Mink van der Weerden.
Australia eased to their second successive men's Hockey victory, taking their goal tally into double figures with a 5-0 victory over Spain, but there was more injury misery for their opponents.
It was a memorable day in the women's Hockey competition with the USA among those making the headlines as they sprang a surprise win in Pool B by recording their first Olympic victory over Argentina, 1-0 at the Riverbank Arena.
Netherlands forward Kim Lammers took her tally to four goals in two matches with another double in a 3-2 win against Japan but the reigning Olympic champions made hard work of their victory.
Australia striker Jamie Dwyer equalled his country's all-time goalscoring record with a hat-trick as the Kookaburras underlined their tag of gold medal favourites with a 6-0 win over South Africa.
The Netherlands recovered from squandering a two-goal lead to just edge out eight-time Olympic Games champions India 3-2 in the men's Hockey competition.
World champions Argentina beat South Africa 7-1 following a five-star first-half performance to underline their credentials as gold medal contenders in the women's competition.
The London 2012 Olympic Hockey competition schedule has been confirmed today, revealing when teams will play each other in the preliminary rounds of the men's and women's tournaments.
