The Tunisian General Labour Union (UGTT), in a statement, said the Iranian-backed group Hezbollah was a "symbol of the (Lebanese) national struggle" against Israel.
Wednesday's move against Hezbollah by the six-nation Gulf Cooperation Council (GCC), led by Saudi Arabia, formed part of "an offensive by foreign and other regional forces to divide the Arab world and destroy its forces", UGTT said.
The head of the Tunisian Order of Lawyers, also a member of the Nobel quartet, called on all "forces in Tunisia and in the Arab world to exert pressure on governments to reconsider their decision".
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Foreign Minister Khemaies Jhinaoui in a televised interview said Tunisia did not support the decision to blacklist Hezbollah, despite Tunisia's Interior Minister Hedi Majdoub signing it.
Tunisia's official stances are announced by the president or the foreign ministry, he said.
The Sunni monarchies of the Gulf, at a time of deteriorating ties between Iran and Saudi Arabia, "decided to consider the militias (of Hezbollah) a terrorist organisation", GCC chief Abdullatif al-Zayani said.
Hezbollah was targeted because of "hostile actions of the militia who recruit the young people" of the Gulf, he said.
Zayani cited "their terrorist acts and incitement in Syria, Yemen and in Iraq", which he said were threatening Arab security.