Thousands of protesters are marching through the streets of Warsaw, in rival demonstrations organized by Poland's opposing liberal and ruling conservative political parties.
Some 10,000 supporters of the country's main opposition liberal Civic Platform party are demonstrating in support of early elections.
Nearby, at least four thousand supporters of the conservative ruling Law and Justice Party are holding a pro-government rally to show support for Prime Minister Jaroslaw Kaczynski.
The government has been struggling with mounting political problems in recent weeks.
The prime minister's twin brother, President Lech Kaczynski, broke up Poland's ruling coalition in late September when he fired his deputy prime minister (Andrzej Lepper) from the cabinet. That move began political wrangling for control of the 460-seat parliament.
Despite losing its majority, the ruling Law and Order party still has enough seats to block a motion to dissolve parliament, which requires a two-thirds majority vote.
Some information for this report provided by AP and Reuters.