Hundreds gathered to protest against the renewed Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP; aka TPP-11) deal in Santiago on Wednesday.
Several people were detained by police after some protesters broke off from the main group and smashed windows and attempted to impede traffic.
The protest was organised by several groups, including agricultural co-operatives who are particularly concerned about provisions they say effectively allow farming industry giants, like Monsanto, to patent plant varieties.
The demonstration came a day after the Chilean Senate's finance commission voted to approve the new CPTPP agreement, which will now move to the constitution and justice commission for a further vote.
The agreement has already been approved by Chile's lower house, the Chamber of Deputies, and now only requires senate approval before ratification.
The new CPTPP contains many of the same provisions as the earlier Trans-Pacific Partnership, which was scuppered after US President Donald Trump withdrew from the deal in January 2017, such as the removal of thousands of tariffs and requiring signatories to provide protections for patents, trademarks, and copyright.
Mexico, Japan, Singapore, Canada, Australia, New Zealand and Vietnam have all ratified the CPTPP, while Brunei, Chile, Malaysia, and Peru have signed the agreement but not yet ratified it.