B787 First Officer reported a rejected takeoff due to receiving an APU fire warning and fire bell during takeoff roll. Flight crew taxied back to gate.

Narrative

During takeoff roll after the thrust set callout we received APU Fire warning on EICAS along with the fire bell. Relief pilots also stated that the APU Fire handle was illuminated. This was followed by the Bottle Disch APU message. The abort was initiated by the Captain around 60 to 70 knots; at which time I reported to Tower that we were aborting followed by the remain seated PA. We then requested instructions to vacate the runway and requested Crash Fire Rescue vehicles to meet us. We exited runway taxied [Taxiways] 1; 2; 3; 4; short of 5 where emergency vehicles met us within 2 minutes. Rejected Takeoff and APU Fire checklist was ran after stopping and a call to the flight attendants to get a status report. The flight attendants reported no smoke or fumes and everything was in order in the cabin. We were instructed to contact ARFF (Airport Rescue and Firefighting) on a separate frequency and ARFF reported no signs of fire or smoke. Captain requested a ARFF vehicle stay with us until we got to gate and this was approved. ELB (Electronic Logbook) Entries were made for low speed abort and Bottle Disch APU.Contacted Ops to try to get a gate and was told it would be at least 30 min wait for Gate XX. We also requested a GPU and ground air because we would not have an APU for power or air conditioning. After a substantial amount of time we were cleared to taxi to Gate XX. Upon arrival to the gate we had to wait about 10 minutes for ground personnel due to a shift change and we also had to wait a long time for ground power to be plugged in. I contacted Operations to remind them that we needed ground power and remind ground personnel that our engines were running.