Tunisia's prime minister said his government has no evidence that the man who stabbed two women to death in Marseille had links to any extremist group.
Meeting on Thursday with his French counterpart in Tunis, Tunisian prime minister Youssef Chahed condemned Sunday's attack, saying "there is no justification for such barbaric acts".
French prime minister Edouard Philippe said the two countries agreed to work more closely together on security and responding to terror attacks and radicalisation.
Mr Chahed said they would notably focus on "preventing the risks inherent in the return of terrorists from hot spots".
French authorities have identified the Marseille attacker as Ahmed Hanachi, a 29-year-old Tunisian.
He was killed by soldiers soon after the stabbings at Marseille's Saint Charles station, which left two young cousins dead after a weekend birthday celebration.
The so-called Islamic State group claimed responsibility, saying he responded to their calls to mete out vengeance for international military operations against the group in Syria and Iraq.
French authorities said Hanachi watched videos of Islamic chants on YouTube but they have not found firm links between Hanachi and IS or signs that he was radicalised.
Five people suspected of helping Hanachi have been arrested.
While French authorities describe Hanachi as a mysterious illegal migrant and IS calls him one of its "soldiers", neighbours in the working class Tunisian neighbourhood where Hanachi grew up painted a different picture.
They described a fisherman with a history of drug problems, abandoned by his wife and with no outward signs of radicalisation.