Witnesses say police in Republic of Congo's capital have fired tear gas to try to disperse protests against a constitutional referendum that could make the country's longtime president eligible for a new term.

Politicians campaigning against the planned Oct. 25 referendum had called for a campaign of "civil disobedience" to begin Tuesday.

Rudel Ganziami, a resident of Brazzaville's southern Bacongo district, said young demonstrators burned tires in the streets and erected barricades Tuesday morning, prompting the police response.

Under current laws 71-year-old President Denis Sassou N'Guesso would be barred from seeking re-election when his second term expires next year. The referendum calls for the limit of two terms to be scrapped as well as changing a regulation stating candidates must be no older than 70 years.