Novak Djokovic began his campaign for a record 23rd men's Grand Slam singles title with victory while world number one Carlos Alcaraz also progressed to the second round at Roland Garros.
Serbia's Djokovic, a two-time champion in Paris, claimed a 6-3 6-2 7-6 (7-1) win over Aleksandar Kovacevic.
US Open champion Alcaraz also came through in straight sets, beating Italian Flavio Cobolli 6-0 6-2 7-5.
The two are in the same half of the draw and could meet in the semi-finals.
After beating American Kovacevic, who is of Serbian heritage, Djokovic wrote on a camera lens: "Kosovo is the heart of Serbia. Stop the violence."
The statement was a reference to recent tension in Kosovo, which declared independence from Serbia in 2008.
Serbia has never recognised Kosovo's independence and there has been violence in the past days following the installation of ethnic Albanian mayors in the north of the country.
Speaking to Serbian journalists, Djokovic, whose father was born in Kosovo, said: "I am not a politician, nor do I intend to enter into debates.
"As a Serb, it hurts me what is happening in Kosovo. Our people have been expelled from the municipalities. This is the least I could do. As a public figure, I feel an obligation to show support for our people and all of Serbia.
"I hear there was a lot of criticism on social media. I don't know if someone will punish me or something like that, but I would do it again. I am against wars and conflicts of any kind.
"Kosovo is our heart, stronghold, the centre of the most important events, the biggest battle took place there, the most monasteries. There are many reasons why I wrote this."
Djokovic was involved in a political row at January's Australian Open after his father, Srdjan, was filmed posing for pictures with supporters of Russia president Vladimir Putin.
Alcaraz's second major bid starts smoothly
Spain's Alcaraz cruised through the first two sets before eventually taking his fifth match point after Cobolli had threatened to force a fourth set.
The 20-year-old will face Japan's Taro Daniel next as he continues his bid for a second major title.
Asked about his approach to the sport after Greek fifth seed Stefanos Tsitsipas yesterday described him as a "breath of fresh air", Alcaraz said: "I heard that Stefanos said he was starting to enjoy his tennis more because of me.
"For me it's the most important thing to enjoy and smile on court."
Djokovic was forced to play a third set tie-break against the 114nd-ranked Kovacevic after being broken as he served for the match in the 10th game.
That came after the crowd had booed his celebration when he broke back against the American midway through the set.
"I played well in the first two sets but then I missed opportunities and lost a little focus," Djokovic, who will face Hungary's Marton Fucsovics next, said.
"But it is also a sign of Aleks' level, which was getting better. When you get to a Grand Slam it is not the opponent who gives you the victory, you have to earn it."
Two-time French Open finalist Dominic Thiem hopes he is on his way back to "tennis heaven" despite falling to a narrow defeat against Argentine Pedro Cachin.
Thiem, who finished runner-up to Rafael Nadal in 2018 and 2019, fought back from two sets down but was ultimately edged out 6-3 6-2 6-7 (1-7) 4-6 6-2.
The 2020 US Open winner's progress was derailed by a wrist injury in 2021 which kept him off the ATP Tour for 10 months but he has since climbed back into the world's top 100.
Discussing the emotions of recent years and his bid to return to the top of the men's game, Thiem said: "It was exactly like that, from tennis heaven to tennis hell, and now hopefully back to tennis heaven.
"It's a very good challenge that I'm facing right now. It's tough obviously but I'm really convinced with the way that I'm going, especially the last six weeks. That's when I started to be really into my career again, really push myself every day to the limit.
"But six weeks is not enough yet to make a deep run here. I have to continue working like that.
"I feel that I'm on the right track again. Today I just failed to reward myself."
Elsewhere on day two, Canada's Felix Auger-Aliassime became the first men's top-10 seed to exit the clay major.
The 10th seed lost 6-4 6-4 6-3 to Italy's Fabio Fognini in his fourth first-round defeat in five years at Roland Garros.
Italian eighth seed Jannik Sinner overpowered France's Alexandre Muller 6-1 6-4 6-1 in one hour and 46 minutes in the night session match on Court Philippe Chatrier.
American 12th seed Frances Tiafoe progressed with a 6-3 6-4 6-2 victory over Serbia's Filip Krajinovic, while there were also victories for top-20 seeds Alex de Minaur and Roberto Bautista Agut.
Australian 18th seed De Minaur beat Belarusian Ilya Ivashka in four sets, while Spain's 19th seed Bautista Agut wrapped up a 7-6 (7-4) 6-1 6-1 win over China's Wu Yibing.
Canadian 26th seed Denis Shapovalov battled to a 6-4 7-5 4-6 3-6 6-3 win over American Brandon Nakashima.
Stan Wawrinka, Switzerland's 2015 champion, lost a two-set lead against Spain's Albert Ramos-Vinolas before rallying in the decider to win 7-6 (7-5) 6-4 6-7 (2-7) 1-6 6-4 win.
BDST: 1216 HRS, MAY 30, 2023