(CNN) Protesters packed part of Moscow on Saturday to protest a bill that would raise Russia's retirement ages to 65 years for men and 63 for women.

Demonstrators with banners and signs rallied in the city center after the country's Communist Party got permission from the mayor's office for the protest, state media outlet RIA Novosti reported.

The Duma, or lower legislative house, passed the measure in a first reading earlier this month. The upper house has yet to consider it.

The current retirement ages are 60 for men and 55 for women. The government has cast raising the retirement ages as necessary to keep pension funds solvent because the proportion of retirees is rising.