The plan, had it succeeded, would have marked a rare attack on federal officials, who have largely escaped the drug-fueled violence that has claimed the lives of many state and local officials.
The intended victims are brothers, one a senator and one a congressman, from the north-central state of Zacatecas. Both Sen. David Monreal Avila and Congressman Ricardo Monreal Avila were warned and placed under protection once the plot was uncovered, based on intelligence information.
The armed gang was arrested Thursday at a hotel in downtown Mexico City, Assistant Attorney General Mariana Benitez told reporters. She did not specify how many were detained, what weapons they were carrying or whether they had any ties to drug gangs.
"Early today the raid was successfully carried out without violence, and apart from the individuals arrested ... guns and communication equipment with which they planned to carry out the assassinations were seized," Benitez said.
Describing the detainees' statements to police, Benitez said "they said they were in Mexico City to kill the legislators."
Benitez did not give any possible motive in the failed plot.
The brutal Zetas cartel has been fighting turf battles and engaging in leadership struggles in Zacatecas, a key trafficking route. Both Monreals are members of leftist parties, and Ricardo Monreal served as Zacatecas governor from 1998-2004.
He later served as a key campaign official for former leftist presidential candidate Andres Manuel Lopez Obrador in his failed bids for the presidency in 2006 and 2012.
In 2009 army troops acting on a tip raided a chile-drying warehouse owned by another brother, Candido Monreal, and found people loading marijuana onto trucks. More than 11.4 tons of the drug were seized at the plant, near the city of Fresnillo, Zacatecas.
The Monreals said the warehouse had been broken into, and Candido was never charged. Ricardo Monreal told reporters later quoted his brother as saying "the (locks) had been broken, and he reported it to police."
That same year, Ricardo Monreal accused the Zacatecas government of being completely infiltrated by drug traffickers. He resigned from the leftist Democratic Revolution Party, which governed Zacatecas at the time, to protest what he called a smear campaign against him.
While state and local police officials, mayors and local prosecutors have often been murdered by drug gangs or rivals in Mexico since 2006, federal officials have seldom been targeted.
A federal congressmen from the southern state of Guerrero was killed in 2011, and prosecutors blamed the killing on a local mayor, who allegedly ordered congressman Moises Villanueva killed because he "got in the way" of the mayor's political plans.
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