The Scot, the back-to-back and reigning Olympic gold medallist in men's singles, knocked out American Frances Tiafoe 7-6, 3-6, 6-1 in a battle between two wildcards.

It was Murray's first match at an ATP Tour event since he won the European Open in Antwerp in October, with the 33-year-old spending much of the past two years on the comeback trail following major hip surgery.

The Masters 1000 tournament, also known as the Western & Southern Open, is taking place at New York's Billie Jean King Tennis Centre this year having been moved from Cincinnati.

Players are remaining in a coronavirus "bubble" ahead of the US Open which is due to begin at Flushing Meadows on August 31.

"I thought I moved well today," said Murray, a two-time Cincinnati Masters winner who saved a set point in the opening tiebreak.

"That was probably the thing I was most happy with and probably the thing I was most apprehensive about going into the match.

"I thought I moved pretty well. 

"My tennis could have been better. 

"I did some things well at the end, but I could definitely improve in terms of my game."

Murray, who won the US Open in 2012, will now meet Germany's fifth seed Alexander Zverev in the second round.

Elsewhere in the men's draw, there was a 6-3, 6-3 win for Canada's 12th seed Denis Shapovalov over Croatia's 2014 US Open winner Marin Čilić.

South Africa's two-time Grand Slam finalist Kevin Anderson knocked out Britain's Kyle Edmund, 7-6, 4-6, 6-3.

Canada's former Wimbledon finalist Milos Raonic defeated American Sam Querrey, 6-4, 6-4.

In the women's event, wildcard Venus Williams was knocked out by Ukraine's 16th seed Dayana Yastremska.

The 40-year-old American legend, a seven-time Grand Slam winner, was beaten 5-7, 6-2, 7-5.

Sixteen-year-old Coco Gauff, widely tipped as one of the future stars of the sport, also missed out as the American lost 6-1, 6-3 to Greece's 13th seed Maria Sakkari.

Kazakhstan's ninth seed Elena Rybakina was a casualty as she fell 7-5, 7-6 to Russia's Ekaterina Alexandrova.

The 11th seed Alison Riske was also beaten as she lost an all-American duel to Amanda Anisimova, 6-3, 6-3.

The women's event is a WTA Premier 5 tournament.

Competition in both draws will continue tomorrow.