Andy Murray survived a scare as he defeated Germany's Philipp Kohlschreiber 6-7 (7-4), 7-6 (20-18), 6-1 in a marathon encounter to enter the semi-finals of the Dubai Championships.

The world number one saved seven match points in a remarkable 38-point tiebreak which lasted over half an hour. Such was the intensity of the moment that the umpire forgot to tell the players to change ends with the score at 15-15. Murray himself pointed out the error two points later, and revealed the umpire's scoring machine didn't provide its reminder: "I don't know if the machines are made to go that high, because it doesn't happen very often."

Playing in his first tournament since a surprise fourth round exit in the 2017 Australian Open, the 29-year-old had a slow start, losing the first set.

However, Murray seemed to be back on track in the second set until Kohlschreiber made a spirited comeback.

Murray had four set points until the German went ahead 9-8. Despite many opportunities to upset Murray, Kohlschreiber lost the second set tiebreak 20-18.

The second set took too much out of the 33-year-old as Murray cruised to victory in the third set in just 30 minutes.

"It was very rewarding to come through a match like that and obviously I'm very pleased to get through it," Murray said as quoted by AFP. "I would have been very disappointed if I'd lost the second set, but also, I didn't feel like I was playing badly."

"I played a poor tiebreak in the first set, but apart from that, I felt I was playing pretty well and he was playing really good stuff.

"I've never played a tiebreak that long ever. Not in juniors, nothing even close to that, I'll probably never play another one like that again. I've have been playing on the tour for 11, 12 years now, and nothing's been close to that."

Despite the loss, Kohlschreiber said he played some of the best tennis of his life.

"Of course losing is always disappointing, but I'm not sad," he said as quoted by the BBC. "I think I played great tennis, one of my best matches. You can be thinking about one or two shots, but it was just a great match. It's well-deserved, he's a great fighter, he never gave up."

Murray, who avoided an early exit unlike Roger Federer and Stan Wawrinka, will now face Lucas Pouille in the semi-finals on 3 March.