The Russian had been training with 11-time champion Rafael Nadal of Spain yesterday only to test positive just hours later.

But Nadal has been given the all-clear to begin his campaign in the ATP Masters 1000 event as he prepares to make his first appearance since losing in the Australian Open quarter-finals in February.

The ATP revealed that Medvedev had been moved into isolation where he will be monitored by its medical team.

"It’s a big disappointment not to play in Monte-Carlo," he said.

"My focus is now on recovery and I look forward to getting back out on Tour as soon and as safely as possible."

Nadal is set to meet Argentina’s Federico Delbonis, who beat Frenchman Adrian Mannarino 7-5 6-1 at the Monte Carlo Country Club today.

"Nadal is absolutely fine," Benito Perez-Barbadillo, publicist for the 20-time Grand Slam champion, told Reuters.

"As we understand the virus does not anyway show before three-four days.

"The next scheduled testing is in three days."

Italian teenager Jannik Sinner who reached the final of the Miami Open booked a blockbuster meeting with world number one Novak Djokovic of Serbia.

Making his Monte-Carlo Masters debut, Sinner recovered from a slow start to defeat 2017 finalist Albert Ramos-Vinolas of Spain 6-3, 6-4.

It will be the first ATP Tour meeting between Sinner and Djokovic, with the Serbian set to compete for the first time since he captured a ninth Australian Open title.

Sinner was one of five Italians to reach the second round today.

Defending champion Fabio Fognini moved past Serbia's Miomir Kecmanovic 6-2, 7-5, while there were also wins for Lorenzo Sonego, Marco Cecchinato and Salvatore Caruso.

Sonego defeated Hungary’s Marton Fucsovics 6-3, 6-4 to extend his unbeaten record on clay this year to 5-0 and advance to the second round where he is due to face Germany’s Alexander Zverev.

Cecchinato converted five of his nine break points to beat German qualifier Dominik Koepfer 6-4, 6-3, while Caruso came from behind to beat Monegasque wild card Lucas Catarina 6-7, 7-6, 6-3 in over three hours.

Miami champion Hubert Hurkacz of Poland needed three sets to complete his two-day encounter against Italy’s Thomas Fabbiano on 6-3, 3-6, 6-3.

The 13th seed is scheduled to meet Dan Evans for a place in the third round after the British number one saw off 2019 runner-up Dusan Lajovic of Serbia 6-3, 6-7, 6-2.

Fourth seed Stefanos Tsitsipas of Greece claimed a 6-3, 6-4 victory over Aslan Karatsev to progress to the third round.

Tsitsipas awaits the winner of Australian John Millman and Chilean 16th seed Cristian Garin for a spot in the quarter-finals.

Garin defeated France’s Felix Auger-Aliassime in a rain-interrupted 7-6, 6-1 first-round clash, while the Millman advanced after a 6-3, 6-3 victory over Frenchman Ugo Humbert.

Elsewhere, Norwegian Casper Ruud won a Scandinavian showdown against Danish wild card Holger Vitus Nodskov Rune 6-2, 6-1, while Spanish ninth seed Roberto Bautista Agut downed American Taylor Fritz 6-2, 7-5.