New coach Luciano Spalletti failed to inspire AS Roma as they were held 1-1 at home by bottom club Verona on his debut on Sunday and Juventus notched their 10th Serie A win in a row by hammering Udinese 4-0 away.
The Greek league leaders confirmed the move but did not give financial details. Local media said Toure would be paid around 2.5 million euros ($2.9 million) for one season.
The victory saw the unfashionable Madrid club tighten their grip on the coveted fourth spot in the table by moving on to 58 points after 36 games, three points clear of nearest challengers Sevilla, who lost to Leganes on Friday.
Lionel Messi fittingly sealed Barcelona's 26th La Liga title on Saturday by coming off the bench to score the goal in a 1-0 win over Levante in front of a jubilant Nou Camp crowd, who celebrated a remarkable eighth league crown in 11 years.
Cristiano Ronaldo bagged his first five-goal haul in Real Madrid's 9-1 hammering of Granada while title-chasing Bayern Munich and Chelsea won again in Germany and England.
News of all that's transpired on and off the football field
Photos from the football matches played in the Serie A, Bundesliga and French Ligue 1 on Sunday
La Liga leaders Real Madrid were thumped 4-0 away by city rivals Atletico Madrid to open up the Spanish title race, while Chelsea strengthened their hold on top spot in the English Premier League after a 2-1 win at Aston Villa.
News of all that's transpired on and off the football field
In England, the celebrations went on at Leicester City as they marked their fairytale Premier League success with another win while champions Juventus' long unbeaten streak in Italy came to an end.
News of all that's transpired on and off the football field
Manchester City have signed French central defender Aymeric Laporte from Spanish club Athletic Bilbao, the Premier League leaders said on Tuesday.
Hegerberg hat-trick fires Lyon to fourth straight Champions League
A summary of Wednesday's matches in the UEFA Champions League.
News of all that's transpired on and off the football field
After a Champagne Sunday, leaders Chelsea got back to the bread and butter of churning out Premier League points with Eden Hazard's header sealing a 1-0 victory at London rivals West Ham United on Wednesday.
Here is the round-up of all the football action across Europe on the weekend
Bayern Munich put upstarts RB Leipzig firmly in their place by sweeping to an emphatic 3-0 home win, with all the goals coming in the first half, in a disappointingly one-sided top-of-the-table Bundesliga clash on Wednesday.
Juventus striker Gonzalo Higuain again showed his killer instinct with two expertly-taken goals in a late 3-1 win at Torino after their less illustrious neighbours had scored first and dominated the Serie A game on Sunday.
UEFA president Michel Platini hit out at FIFA chief Sepp Blatter on Friday, saying the Swiss has stopped serving the cause of football.
News of all that's transpired on and off the football field.
A weekend of surprise results across Europe's big leagues saw Bayern Munich's unbeaten run come to an end, Napoli knocked off top spot in Serie A and Manchester City toppled in the Premier League where Leicester City are the new leaders.
Real Madrid lifted the FIFA Club World Cup for a record fourth time on Saturday after thrashing local side Al Ain 4-1 in the final in Abu Dhabi with the help of impressive distance strikes in either half from midfielders Luka Modric and Marcos Llorente.
Manchester United dropped further down the table after losing 5-3 against newcomers Leicester City. Barcelona and Real Madrid scored 13 goals between them during a memorable La Liga weekend, when Cristiano Ronaldo netted a hat-trick.
A summary of Wednesday night's matches inthe UEFA Champions League.
News of all that's transpired on and off the football field
Real Madrid edged past Sporting Lisbon 2-1, while Juventus came from behind to secure a 3-1 win at Sevilla and Borussia Dortmund crushed Legia Warsaw 8-4 to set a record for the most goals scored in a Champions League match.
News of all that's transpired on and off the football field
News of all that's transpired on and off the football field
Photographic summary of the football matches played across Spain, Italy and France
News of all that's transpired on and off the football field.
Two goals from Thomas Mueller and one from substitute Mario Goetze helped Bayern Munich kick off their Champions League campaign with an impressive 3-0 victory over Olympiakos.
Lionel Messi came off the bench to inspire Barcelona to a 3-1 win over a dogged Leganes side on Sunday, creating one goal and scoring another to keep the Catalans five points clear at the top of La Liga.
News of all that's transpired on and off the football field
News of all that's transpired on and off the football field
News of all that's transpired on and off the football field
Images from Tuesday night's UEFA Champions League group stage matches.
News of all that's transpired on and off the football field
News of all that's transpired on and off the football field
Images from Champions League matches played across Europe on Tuesday