The sale of Rugby World Cup tickets on a first-come, first-served basis began Saturday, with organizers urging fans to get in quick so as not to miss out.

Sales of tickets for all 48 matches began online at 10 a.m. Japan Standard Time and will continue until either all available tickets sell out or the sales period ends just before midnight on March 31.

Tickets for pool games involving hosts Japan, reigning world champion New Zealand, England and Ireland and knockout stage matches are extremely limited, according to organizers.

The organizers expect the ticketing website to experience high traffic levels after sales commence. The organizers encourage fans to secure their tickets using the real-time ticket availability indicator on the site.

An official source said over 1.1 million of the 1.8 million tickets for the Sept. 20-Nov. 2 tournament were already snapped up in previous phases.