Mexico's outgoing president Andrés Manuel López Obrador has hailed the approval of controversial reforms to allow voters to elect all judges, saying they would be an "example to the world".
Mr López Obrador had pushed hard for the constitutional changes that will make Mexico the world's first country to allow voters to elect judges at all levels.
The leftist leader, who will leave office on 1 October, accuses the current judicial system of serving the interests of the political and economic elite.
"It's very important to end corruption and impunity," Mr López Obrador told a news conference.
"We will make great progress when it is the people of Mexico who freely elect the judges, the magistrates, the justices," he added.
The reform was approved with 86 votes in favour and 41 against, garnering the two-thirds majority needed to amend the constitution, in an upper chamber dominated by the ruling Morena party and its allies.
Debate on the reform had sparked mass demonstrations, diplomatic tensions and investor jitters.
Senate leader Gerardo Fernández Noroña declared a recess after demonstrators stormed the upper house and entered the chamber, chanting: "The judiciary will not fall."
Politicians were forced to move to a former senate building, where they resumed their debate as demonstrators outside shouted: "Mr Senator, stop the dictator."
Mr López Obrador, who wanted the bill approved before he is replaced by close ally Claudia Sheinbaum, said that protesters were protecting the interests of the "powerful".
"What most worries those who are against this reform is that they will lose their privileges because the judiciary is at the service of the powerful, at the service of white-collar crime," he said.
Opponents, including court employees and law students, have held a series of protests against the plan, under which even supreme court and other high-level judges, as well as those at the local level, would be chosen by popular vote.
Around 1,600 judges would have to stand for election in 2025 or 2027.
"This does not exist in any other country," said Margaret Satterthwaite, United Nations special rapporteur on the independence of judges and lawyers.
"In some countries, such as the US, some state judges are elected, and in others, such as in Bolivia, high-level judges are elected," she told AFP.
Mexico's overhaul puts it "in a unique position in terms of its method for judicial selection," Ms Satterthwaite said ahead of the vote.
In an unusual public warning, supreme court chief justice Norma Piña said that elected judges could be more vulnerable to pressure from criminals, in a country where powerful drug cartels regularly use bribery and intimidation to influence officials.
"The demolition of the judiciary is not the way forward," she said in a video released on Sunday.
Ms Piña said last week that the top court would discuss whether it has jurisdiction to halt the reforms, though Mr López Obrador has said there is no legal basis for it to do so.
The reforms were passed last week in the lower house by ruling party politicians and their allies, who were forced to gather in a sports centre because access to congress was blocked by protesters.
The United States, Mexico's main trading partner, has warned that the reforms would threaten a relationship that relies on investor confidence in the Mexican legal framework.
The changes could pose "a major risk" to Mexican democracy and enable criminals to exploit "politically motivated and inexperienced judges," US Ambassador Ken Salazar said last month.
Financial market analysts say investor concerns about the reforms have contributed to a sharp fall in the value of the Mexican currency, the peso, which has hit a two-year low against the dollar.
Ms Satterthwaite has also voiced "deep concerns" about the plan, calling access to an independent and impartial judiciary "a human right essential for protecting rights and checking power abuses".
"Without strong safeguards to guard against the infiltration of organized crime (in the judicial selection process), an election system may become vulnerable to such powerful forces," she said.
Human Rights Watch had urged politicians to reject what it called the "dangerous proposals," saying they would "seriously undermine judicial independence and contravene international human rights standards".
