The 31-year-old won 6-7 (5-7) 6-3 7-6 (7-4) in a match that finished at 03:02 local time.

Murray will play Alex de Minaur of Australia in the quarter-finals - his first since Wimbledon in 2017.

He is playing only his third tournament since hip surgery in January.

Three-time Grand Slam champion Murray - now ranked 832 in the world - lost the first set in one hour and six minutes, having taken a 5-0 lead in the tie-break before losing seven points in a row.

He broke Copil twice in the second set to take it in 45 minutes and looked set to take the third comfortably when he secured a break in the sixth game to move 4-2 up.

But the Romanian, ranked 93rd, immediately broke back before holding serve to level the match, before Murray's fitness prevailed in the deciding tie-break.

An emotional Murray then sat courtside and sobbed into his towel.

The tournament's previous latest finish was 02:27 local time.