French Foreign Minister Alain Juppe voiced concerns on Wednesday over the arrests of Russian opposition protesters following disputed parliamentary elections, saying the numbers were increasing.

"We are worried by the arrests and detentions that are increasing since the elections results have been known," Juppe told reporters on the sidelines of talks among NATO foreign ministers in Brussels.

France has urged Moscow to investigate allegations of widespread irregularities during the weekend elections won by Prime Minister Vladimir Putin's party with a reduced majority.

"We want to have clarity regarding the conditions under which these elections took place since there are severe assessments about their organisation," Juppe said.

Former Soviet leader Mikhail Gorbachev on Wednesday called for Russia's elections to be re-run due to fraud and the opposition vowed to hold new rallies contesting the results.