The Florida-based blood centre OneBlood will be collecting donations at the bands' sold out concert at the Bayfront Park Amphitheater.

Fans hoping to give blood during the four-hour drive must be at least 16, "weigh 110 pounds and be sober while donating".

Those who are 16 will need a parent's presence or written consent.

A gunman opened fire in packed Orlando club Pulse on Saturday night, killing 49 people and injuring 53 more before being killed during a shootout with police officers.

The attack is the worst mass shooting in U.S. history.