French authorities have seized a small aircraft belonging to ousted Tunisian President Zine al-Abidine Ben Ali's family at an airport near Paris, the Paris prosecutor's office said on Tuesday.

The European Union agreed on Monday to freeze assets belonging to Ben Ali and his wife after he was driven from power last month in a popular revolt. France had already opened a preliminary investigation into his assets on its soil.

The plane was seized as part of the investigation, opened after non-governmental organisations filed a lawsuit seeking to get Ben Ali's assets in France returned to Tunisian authorities if proven that they were obtained illegally.

A police source said the aircraft was a small Bombardier jet. It was seized at Le Bourget airport, where it had been parked for several days, the prosecutor's office said.

The three NGOs, Transparency International, Sherpa and the Arab Commission for Human Rights, say the deposed Tunisian leader and his family own valuable property in prime Parisian locations as well as big bank assets.

Ben Ali and his family built up interests in many Tunisian companies and industries during his two decades in power, including in hotels, banks, tuna exports, construction, newspapers and pharmaceuticals.-Reuters