PARIS (AFP/REUTERS) - A man who holed up in a post office in a suburb northwest of Paris with two hostages on Friday surrendered and has been arrested, a police source said.

"There was no assault, the man gave himself up", the source said, adding that the hostages were "shocked but not injured".

French police arrested 12 people earlier on Friday suspected of helping militant Islamist gunmen in last week's killings in Paris. There have been numerous false alerts across the city since the attacks.