"URGENT: I inform the country and worldwide public opinion that I am being notified at this very moment of a BAN for 15 years", tweeted Capriles. Around 4,000 people attended the demonstration.
Capriles lost narrowly in the 2013 election that brought Maduro to the presidency after the death of his mentor Hugo Chavez - father of Venezuela's "socialist revolution".
On Saturday Caracas-area mayor David Smolansky denounced the presence of a previously unseen red gas used to scatter thousands of protesters who in recent days have taken to the streets against Mr Maduro.
AFP reporters also witnessed a National Guard soldier lying unconscious after having been struck by a large rock.
"Urgent! We were bombed inside the building, now the firefighters are working", Capriles said on Twitter. We'll see you on the streets of Venezuela @nicolasmaduro.
Demonstrators clash with riot police during a rally in Caracas, Venezuela, April 8, 2017.
"This thing that they just did to Capriles is the product of tyranny", said Adel Rincones, 61, who clutched a sign that read "Venezuela is wounded in the heart with hunger, misery, corruption, dictatorship".
"People are exhausted of so much corruption, hunger and poverty", said Vanessa Garcia, 37, an optometry student.
Two people were reported injured by rubber bullets in San Cristobal, an opposition hotbed near the country's border with Colombia.
The country has undergone three attempted military coups since 1992.
Intelligence Services chief Gustavo Gonzalez said some leaders of a "fascist terrorist cell" were taken into custody for fomenting Saturday's unrest.
"This is all part and package of the internal coup", Capriles said on Twitter. On the same day, at least 26 people were injured in the protest near the University of Carabobo in the country's north. Maduro didn't comment Friday during an appearance on state TV about the comptroller general's order containing the ban on Capriles' ability to run.
Capriles said that he would appeal the decision and stay in his job as governor, which he has held since 2008.
Thousands of Maduro opponents marched on Thursday to protest a decision by the administration-leaning top court to assume control of the opposition-led congress in what demonstrators said was a lurch toward dictatorship.
The court later reversed the rulings after an worldwide outcry, but kept in place other measures limiting the assembly's powers.
While the court eventually reversed the ruling amid growing pressure, the decision galvanized the opposition and set off tense protests throughout the following week.
Protesters are demanding the dismissal of all seven justices of the Venezuelan Supreme Court. But the ombudsman's office blocked the move.
Anger erupts in Caracas as protesters battle Venezuelan authorities in the capital city. There are shortages of food, medicines and basic goods.
Still, others have been motivated by the escalating political crisis and the opposition coalition is putting on a more dynamic and coordinated front than usual. That decision was walked back amid fierce domestic and global criticism, but opposition leaders say it revealed the government's authoritarian nature.