About 2,000 people have gathered on Bishkek's central square, calling for immediate constitutional reform and early presidential elections.
On Wednesday, the opposition erected roadblocks and demanded access to national television.
The United Front of Kyrgyzstan, a major opposition movement, claimed it had blocked a major highway connecting Bishkek with Lake Issyk-Kul, and called on President Kurmanbek Bakiyev and the governor of the Issyk-Kul Region to resign.
With the arrival of additional supporters from the provinces, an estimated 3,000 protesters then moved peacefully downtown in a column, led by heads of the country's most prominent NGOs and chanting anti-presidential slogans.
The rally continued near the national television headquarters with calls for fair media coverage of the street action as police stood by.
Since April 9, the opposition has been demanding the adoption of a new Constitution curbing presidential powers and accusing pro-Bakiyev MPs of foot-dragging.
Pressured by the new prime minister, Almaz Atambayev, who helped draft the new Constitution, Bakiyev signed it April 10 and handed it over to the legislature. However, lawmakers have resisted debate, citing street pressure.
