Paris: Andy Murray lifted his level to his best of the tournament with a 6-3, 6-4, 6-4 sprint into his fourth consecutive quarter-final at the French Open.

Murray schooled 21-year-old rising Russian Karen Khachanov as the youngster played in Paris for the first time.

The two-hour win was the 650th Tour-level victory of Murray's career, with the top seed standing 650-181 overall. The Paris victory marked his 20th match win of the season

Murray paid tribute to the victims of recent terror attacks in England post-match and was given a standing ovation by the crowd.

"Obviously there was a terrible tragedy in London, and in Manchester six or seven days ago. Paris has had its problems too in recent years," Murray said.

"I am sure everyone will join me ... we share our thoughts and prayers with everyone who has been affected. It's obviously something that has affected large parts of Europe.

"I appreciate everyone still coming out to support the tennis. I am grateful that I can still perform in front of everyone."

While the UK was on his mind, so was the improvement in his game over the past week and it's a confident world No.1 that heads into the quarters against Kei Nishikori.

"I think today was probably the best I have played overall," Murray said. "Each match I feel like I played better. I have hit the ball cleaner and started to hit the right shots at the right moments. [I have] come a long way the last 10 days or so."

Murray will next play Japanese eighth-seed Nishikori, who recovered to beat veteran Spaniard Fernando Verdasco 0-6, 6-4, 6-4, 6-0 and Murray was wary of the resurgent 2014 US Open finalist.

For his part Nishikori has only ever beaten Murray twice but one of those wins came at last year's US Open when Nishikori got home in five sets.

Joining them in the quarters are 2015 French Open champion Stan Wawrinka and 2014 US Open champion Marin Cilic.

Wawrinka beat 15th seed Gael Monfils 7-5, 7-6 (9-7), 6-2 to earn a ninth win from 10 meetings with French opponents at the tournament.

"It was a mental challenge, it's never easy to play Gael in Paris," Wawrinka said. "It was windy, tough conditions. It was important for me to focus, be tough with myself and fight for every point."

Cilic advanced as Kevin Anderson retired hurt with a leg injury, when trailing the Croat 6-3, 3-0.

Halep laud's Cahill's tough love

Simona Halep credits the tough love of esteemed Australian coach Darren Cahill as the key to her stunning transformation from fragile firebrand to new French Open title favourite.

The Romanian third seed continued her resurgence to storm into the quarter-finals on Monday with a 6-1, 6-1 dismissal of Spanish claycourter Carla Suarez Navarro.

The one-sided victory was her 13th in 14 matches since reuniting with Cahill after the pair briefly split following a heated player-coach on-court exchange in Miami in March.

The self-confessed hot-head said Cahill's decision to walk away and return home to Australia after her Miami meltdown was the wake-up call she needed.

"I just felt that it was like a shock, because I lost the coach," Halep said after setting up a last-eight showdown with Ukraine's fifth seed Elina Svitolina, the only player to beat the world No.4 on clay in 2017.

"So I have just to improve in this way because he never had something to complain about my game and about the work that I do because I'm working, but just with my attitude."

After their high-profile bust-up, Cahill told Halep "we will talk after Paris", but she pleaded for the coach who helped Lleyton Hewitt become the youngest-ever men's year-end No.1 and then Andre Agassi to become the oldest to snare the top ranking to return to her box.

"He said yes because I improved a lot, and he saw that I really wanted to change," Halep said.

"Now I'm happy that I can be positive on court, and I will never be negative like I was in Miami because ... when I saw the video, I felt ashamed about what I did."

Runner-up to Maria Sharapova at Roland Garros in 2014, Halep plays Svitolina on Wednesday for a place in the semi-finals.

On Monday Svitolina trailed Petra Martic 5-2 in the deciding set before reeling off five straight games to snatch a 4-6, 6-3, 7-5 victory over the Croatian qualifier.

World No.3 Karolina Pliskova overcame an awful start to beat Veronica Cepede Royg of Paraguay 2-6, 6-3, 6-4  to reach the quarters for the first time.

Pliskova, the 2016 US Open runner-up, will take on Caroline Garcia of France for a place in the semi-finals.

Garcia overcame her own nerves to beat countrywoman Alize Cornet 6-2, 6-4 and become the second Frenchwoman at this year's tournament to make the quarters, along with Kristina Mladenovic.

AAP