LaLiga: Atletico Madrid come from behind to beat Valencia 3-1; Barcelona down Elche 2-0 without suspended Lionel Messi
Coming from behind for a second straight time, Atletico defeated Valencia 3-1 on Sunday to strengthen their hold on the league lead entering the second half of the season.
Dembele will join Atletico until the end of the season when the club will have the option to buy him permanently for around 35 million euros.
Angel Correa and Saul Niguez scored as Atletico Madrid extended their Spanish league lead with a 2-0 victory over Sevilla.
Valencia were starting their pre-season preparations this week under new coach Javi Gracia, who was appointed two weeks ago following the sacking of Albert Celades in June.
Champions League: Atletico Madrid heave sigh of relief as remaining squad members test negative for COVID-19
Tests at the weekend had revealed two coronavirus cases at the club, which Atletico confirmed on Monday to be players Angel Correa and Sime Vrsaljko.
Correa is the second Atletico player to be injured in training this week after record signing Joao Felix sprained the medial ligament in his left knee on Monday.
Atletico Madrid secured a much-needed 1-0 victory against Granada which was inspired by returning captain Koke.
LaLiga: Real Madrid enter winter break behind leaders Barcelona after draw against Athletic Bilbao; Atletico Madrid beat Real Betis
Zinedine Zidane will face questions about Real Madrid´s scoring slump after it was held 0-0 at home by a tame Athletic Bilbao on Sunday. The slip at the Santiago Bernabeu came after drawing 1-1 at Valencia and 0-0 at Barcelona over the past week.
LaLiga: Alvaro Morata nets his sixth goal in all competitions as Atletico Madrid come from behind to defeat Espanyol
Morata thumped home his fifth league goal of the season just before the hour mark to put Atletico in front in Madrid after Sergi Darder had shocked the Wanda Metropolitano with fine opener seven minutes before the break.
Atletico Madrid led 5-0 at half time and were 6-0 before Real Madrid got on the scoreboard before a packed house in East Rutherford, New Jersey.
Karim Benzema, Gareth Bale guide Real Madrid to easy win over AC Milan in friendly ahead of Super Cup tie
Karim Benzema and Gareth Bale were on target as European champions Real Madrid defeated AC Milan 3-1 in a friendly on Saturday just four days from their UEFA Super Cup clash with city rivals Atletico.
La Liga: Lionel Messi produces moment of magic as solid Barcelona leave uninspired Atletico Madrid behind
In what was touted as a match between two of La Liga's most in-form men, Messi outshone Griezmann with ease, providing the decisive contribution that helped decide the tie.
La Liga: Surging Atletico Madrid visit stumbling Barcelona for crucial clash that could define title race
La Liga title race is well and truly back on and a poor February for Barcelona has ensured that the match with Atletico will be an evenly-fought contest.
La Liga: Atletico Madrid defender Diego Godin loses three teeth after clash with Valencia goalkeeper Neto
Atletico Madrid defender Diego Godin lost three of his teeth after being caught full in the face by Valencia goalkeeper Neto during Sunday's La Liga encounter, his club said.
Barcelona are now nine points clear at the top of the table from Atletico Madrid, who beat third-placed Valencia 1-0 at the Wanda Metropolitano.
La Liga: Lionel Messi's late goal helps Barcelona claim comeback win over Alaves, Atletico Madrid beat Las Palmas
Barcelona escaped a scare on Philippe Coutinho's first start as Lionel Messi struck with a trademark free-kick to help his side beat Alaves 2-1.
Playing in front of a sparsely populated Wanda Metropolitano, it took dominant Atletico until the 57th minute to extend their 4-0 first leg lead, Yannick Carrasco meeting Diego Costa's cutback and slotting home the opener.
Atletico's transfer ban ended last week and Costa was playing his first league game since rejoining the Spanish club from Chelsea.
Antoine Griezmann returned to form with a stunning overhead kick and assist for Kevin Gameiro to beat Roma 2-0 on Wednesday.
La Liga: Atletico Madrid boss Diego Simeone vows to defend under-fire Antoine Griezmann 'to the death'
Atletico Madrid coach Diego Simeone insisted he will defend off-colour star forward Antoine Griezmann "to the death", as long as he remains an Atletico player, after Saturday's 0-0 draw against local rivals Real Madrid.