Japan, the three-time world champions, the London 2012 Olympic bronze medallists and currently ranked third in the world, were shocked as they were beaten by 37th ranked Azerbaijan. 

The Azeris, who qualified for the tournament for the first time since 2006 by topping Pool J of the European qualifiers, twice came from behind in this Pool D match. 

They lost the opening set 25-17 but bounced back to take the second 25-20, only for Japan to regain the initiative, winning the third 25-20.

Azerbaijan then won the fourth 25-12 before securing victory 15-9 in the fifth and final set. 

Polina Rahimova led the way for Azerbaijan with 33 points, followed by Kseniya Kovalenko with 15.

"I am really happy with this victory, not only because of the tireless efforts and attitude of the team on the court, but also because we managed to beat one of the favourite teams of the tournament," said Azerbaijan coach Aleksandr Cherviakov.

Hosts Italy made a comfortable start as they beat Tunisia 25-11, 25-13, 25-8 before a passionate capacity 10,000 crowd at the PalaLottomatica in Rome. 

Cristina Chirichella top-scored for the Italians, who are looking to become the first hosts to win the world title since Japan in 1967.

But they - and everybody else - faces a tough task against Russia, the defending two-time champions. 

Russia's Tatiana Kosheleva smashes as the defending two-time champions opened their campaign against Thailand in Verona ©Getty Images

The Russians beat Thailand 25-18, 25-19, 25-22 at the PalaOlimpia in Verona in their Pool C encounter, meaning they have now 23 of their last 24 World Championship matches, a run stretching back to their bronze medal match against the 2002 tournament in Germany.

Russia are looking to put behind them the disappointment of London 2012 where, after starting the tournament as favourites, they failed to win a medal following a 3-2 defeat to Brazil in the quarter-finals.

The defeat had tragic consequences as a month later the team's coach Sergey Ovchinnikov committed suicide.  

Brazil, meanwhile, who went onto win the Olympic gold medal at London 2012, started their campaign brightly, beating Bulgaria 25-19, 25-22, 25-16 in Pool B, with Sheilla scoring 15 points in the match at the PalaTrieste in Trieste. 

The Brazilians have never won this tournament, finishing runners-up three times, including in the last two editions, where they have been beaten on each occasion by the Russians.

They are also looking to make up for the disappointment of their men's team, beaten by hosts Poland in the final of the men's World Championships, which ended in Katowice on Sunday (September 21).

Brazil fans turned out in numbers to cheer on the Olympic champions as they beat Bulgaria 3-0 in their opening match in Trieste ©Getty Images

The United States, who are in the same Pool as the Russians, lost their opening set 25-19 to Mexico but bounce back 25-11, 25-20, 25-14 to triumph in Verona. 

A total of 24 countries are competing in the Championships, which is being held in six cities across Italy. 

The tournament is due to conclude on October 12 with the final at the Mediolanum Forum in Milan.

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