Four politicians were arrested and three others were being sought in an anti-corruption sting in a Rio de Janeiro town, officials said Wednesday, describing it as an example of other operations that are under way.

Among the seven arrested or sought were the mayor, the leading candidate for mayor and the head of the city council in Guapimirim, a working class town of about 52,000 people in the foothills of Rio de Janeiro's mountains.

Authorities said 11 other suspects also were indicted in a scheme that investigators allege illegally siphoned off at least $24 million in public funds over four years. The charges include fraud, corruption and racketeering.

The investigation is not an isolated case, prosecutor Antonio Campos Moreira said at a news conference.

"We have a number of similar investigations looking into city halls," Moreira said.

Brazil, which has long ranked toward the bottom of Transparency International's Corruption Perception Index, has been taking steps to improve accountability and practices in government. In the past few years, the government has created oversight bodies such as the CGU, which audits and promotes transparency in the executive branch, and the CNJ, which oversees the judiciary.

Seven members of President Dilma Rousseff's Cabinet have given up their posts or were pushed out following corruption allegations.

These efforts have been largely concentrated at the federal level, however, with very little happening at the state and municipal levels, said Carlos Abramo, head of Transparencia Brasil, a group not connected to Transparency International that focuses on anti-corruption efforts.

"Brazil is a very decentralized state, in which states and municipalities have total autonomy," Abramo said. "At that level you can have total confusion. The lack of administrative competence is widespread."

In the case of Guapimirim, one family, of which the mayor was part, has held control for years. According to court documents, city council members received monthly payments of up to $35,000 to support the reigning coalition.

During the Sept. 7 holiday weekend, groups in dozens of cities across Brazil are planning marches to call for clean government.

Carla Zambelli, organizer of one of the group, NasRuas, or InTheStreets, says marches are expected in 69 cities.

Among their specific demands are the end to secret voting in the legislature and justice in the cash-for-votes trial involving the governing Workers' Party that is currently before the Supreme Court. In that case, the party is accused of illegally paying legislators a monthly stipend to support government projects.

"Brazil is among the countries that pay the highest taxes, but our security, education and health services are terrible," said Zambelli. "We agree with paying taxes, but we want to see it come back to us in services."