MOSCOW: Roberto Mancini's Zenit St Petersburg saw their unbeaten start to the Russian league season ended in a 1-0 home defeat to lowly Arsenal Tula on Sunday.
Zambian striker Evans Kangwa's goal set Arsenal on their way to the second consecutive league win and their first ever victory over the Saint Petersburg club.
Despite the defeat Zenit remained top of the table, two points clear of Lokomotiv Moscow, who also suffered a 1-0 defeat at Ufa.
Last season's runners-up CSKA Moscow, who beat Krasnodar 1-0 on Saturday, sit third, two points further back.
Zenit dominated from the start but their only chance in the opening period came in the 40th minute when Alexander Erokhin forced Arsenal 'keeper Vladimir Gabulov into a diving save with a low shot from the edge of the area.
Six minutes after the break former Chelsea back Branislav Ivanovic sent the ball into the net with a header but his goal was ruled offside.
Halftime substitute forward Artem Dzyuba also saw his 67-minute goal disallowed by the referee for the same reason.
In the 73rd minute Kangwa put the visitors in front, firing the ball home from the edge of the six-yard box off a razor-sharp cross by Kirill Kombarov.
Zenit replied positively but a combination of poor finishing and the good goalkeeping by Gabulov left the scoreline unchanged.
"Zenit were the better side today but we've been waiting for our chance and luckily managed to convert it when it came," Arsenal manager Miodrag Bozovic said. "It's a very necessary win for us as we desperately needed points."
Zenit's closest chasers Lokomotiv Moscow also slumped to a narrow defeat at Ufa.
Ufa Nigerian striker Sylvester "Sly" Igboun was the hero as he scored the winner with 14 minutes remaining.
"Today we've played really well especially in defence," Ufa head coach Sergei Semak said.
"We still experience difficulties in attack as we managed to convert only one of our chances but in general I'm pleased with my team's performance."