Moments after teammate and 100 meter silver medalist Veronique Mang was disqualified for a false start, Soumaire surged to the front of the field from the outside lane to win the race in a European season's best time of 22.32 seconds.
Ukraine's Yelizaveta Bryzhina took silver as the top two passed Aleksandra Fedoriva just as the Russian seemed set for gold when she led coming out of the bend. Russian women had won five medals on Friday night.
Poland picked up its first gold thanks to Marcin Lewandowski's 800 meters win while Belarus' Andrei Mikhnevich edged Olympic champion Tomasz Majewski of Poland and defending champion Ralf Bartels of Germany for shot put gold.
“After some difficult seasons I'm back where I want to be,” said former world champion Mikhnevich, whose second throw of 21.01 meters edged Majewski's by 1 centimeter.
Jessica Ennis of Britain maintained a slim heptathlon lead of 18 points over Olympic champion Nataliya Dobrynska of Ukraine going into the final event.
Ennis managed a personal-best throw of 46.71 meters in the javelin to hold on to the lead ahead of the 800-meter run.
Germany's Jennifer Oeser was third with 5,751 points.
Earlier, Zivile Balciunaite of Lithuania won the women's marathon while 50-year-old Merlene Ottey made history as the oldest athlete to compete at the event when she ran in the 4x100 women's relay.
Balciunaite went around the streets of Barcelona in 2 hours, 31 minutes, 14 seconds to earn her first major triumph. Nailya Yulamanova of Russia won silver in 2:32:15 and Anna Incerti of Italy took bronze in 2:32:48.
“I love to run in the heat, it suits me very well,” said Balciunaite, who slowly worked her way up the field before taking the lead for good after 30 kilometers. “The circuit helped a lot as well - no hills, no turns, just perfect.” Lewandowski hung on the heels of Britain's Michael Rimmer going around the final bend before moving ahead of the Briton to take it in a time of 1:47.07 at Barcelona's Olympic stadium. Poland's Adam Kszczot took the bronze.
Ottey, a naturalized Slovenian of Jamaican origin, surpassed the age record held by 47-year-old French marathon runner Nicole Brakebusch-Leveque. But Slovenia failed to get out of the heats, led by Russia.
“It's right up there with all the medals I have won,” said Ottey, who has won 29 medals in major competitions, including seven Olympic Games, starting at Moscow in 1980.
“It didn't cross my mind (at 40) that I would still be running now. I thought I would retire.” France advanced to the men's 4x100 relay final on Sunday despite Christophe Lemaitre, who won the 100 and 200 dashes, sitting out qualifying. Martian Mbandjock, who won bronze in the 100 and 200, anchored France. Germany was fastest in a time of 38.75.
