A little over three weeks since Djokovic was defaulted in the US Open fourth round for hitting a line judge with a ball, the Serb was as cool as a cucumber as he outclassed the young Swede.

Only a smattering of fans were inside Philippe Chatrier Court as Djokovic won the opening set in 20 minutes.

Djokovic did drop serve early in the second set when an attempted drop shot fell short but there was no angry response this time, just an ironic chuckle.

The 33-year-old then led the applause for Ymer when he played a sensational between-the-legs winner Nick Kyrgios would have been proud of in the sixth game.

But it was one-way traffic as Djokovic polished off the second set with his trademark clean hitting.

The 80th-ranked Ymer, facing a world No.1 for the first time, stuck manfully to his task in the third set and Djokovic became a little sloppy as he handed back a service break with a double-fault after which he flexed his hand.

Top seed Djokovic, bidding for a second French Open title, glared at someone in the crowd in the following game and re-focused to reel off the last three games for victory.

Elsewhere, No.13 seed Andrey Rublev recovered from two-sets down to beat American Sam Querrey.

The Russian, who won the final of the Hamburg Open on Sunday, came through 6-7 (7-5) 6-7 (7-4) 7-5 6-4 6-3 in a match which lasted almost three-and-a-half hours.

Italian seventh seed Matteo Berrettini beat Canada's Vasek Pospisil 6-3 6-1 6-3, Chile's Christian Garin, seeded No. 20, defeated Philipp Kohlschreiber 6-4 4-6 6-1 6-4 and Australian Marc Polmans ended the hopes of home player Ugo Humbert with a 6-2 6-2 3-6 6-3 win.

No. 22 seed Dusan Lajovic progressed after a 6-4 7-6 (7-4) 4-6 6-1 victory over Gianluca Mager while South African Kevin Anderson is also into the second round following his 6-2 6-3 6-4 win over Laslo Djere.

In Tuesday's later matches, world No.6 Stefanos Tsitsipas survived a scare as he fought back from two-sets down to defeat Jaume Munar 4-6 2-6 6-1 6-4 6-4.

The Greek, runner-up to Rublev in Hamburg, produced a string of unforced errors as the 109-ranked Spaniard took control of the match before digging deep to mount a strong recovery.

There was more disappointment for the few French fans at the Paris venue as Gilles Simon was beaten 6-2 7-5 5-7 6-3 by Canada's Denis Shapovalov and No.10 seed Roberto Bautista Agut defeated Richard Gasquet 7-6 (7-5) 6-2 6-1.

Grigor Dimitrov, the 18th seed, progressed with a 6-3 6-2 6-2 win over Gregoire Barrere.

Australian Associated Press