Young triathletes complete the swim stage at Narrowneck Beach. Photo / APN

More New Zealand children than ever have competed in the Weet-Bix Kids Tryathlon series, and yesterday's North Shore event reached capacity.

Yesterday morning 2250 children aged 7 to 15 swam, biked and ran near a Narrowneck Beach Reserve bustling with athletes and their supporters.

They were among a total of 21,183 New Zealand children participating across the whole series - a record for the event, a spokesman said.

Sports stars Cameron Brown, Alison Shanks and Maddie Dillon handed out medals to children as they crossed the finish line.