Police in riot gear stormed a rally in Bishkek, Kyrgyzstan, on Sunday, removing hundreds of protesters by truck.
Police went to nearby streets using the Ala-Too square, thousands of opponents to disperse Strand grenades, tear gas and water cannon.
About 120 people were injured, half of them law enforcement, the health ministry said in a statement.
The condition of some people is serious but no deaths have been reported.
Only four of the 16 parties in Sunday’s election passed the 7% threshold for entry into parliament, three of which have close ties with President Soronbay Jinbekov.
Groups close to the president have been accused of buying votes and intimidating voters – according to international monitors, are “credible” and cause “serious concern”.
On Monday, the 12 opposition parties jointly announced that they would not recognize the results of the vote.
President Jinbekov’s office later said it would meet with leaders of all 16 parties participating in the election on Tuesday with the aim of easing tensions.
Opposition candidates also called on the Central Electoral Commission to cancel the election results.
One candidate, Riskeldi Mombekov, told a crowd of more than 5,000,000 protesters on Monday: “The president has promised to monitor the election in good faith. He has not kept his word.”
Mr Mombekov’s party, Ata McCann, was confident of entering parliament, but in the end it was one of eight parties that missed the threshold. Ata McCain leader Janar Archive suffered a leg injury during Monday’s protest.
Protesters were also calling on President Jinbekov to resign.
Thomas Bozrep, head of the Organization for Security and Cooperation in Europe’s (OSCE) election observation mission, said in a statement that although the vote was “generally streamlined”, allegations of vote-buying were “serious concerns”.
How the protest grew
Almaz Tichoroyev, BBC News, Bishkek
Police water cannon on the demonstrators, using stun grenades and tear gas.
They first used force to disperse protesters in the main square, but police continued their pursuit as mobs infiltrated other streets in Bishkek.
There have also been reports of injuries – between protesters and police. Among those injured was an opposition leader, General Archive.
Around 2,000 people were protesting in Ala-to-Square and the demonstration was largely peaceful for most of the day. But at about 20:10 local time (14:10 GMT), a small group of protesters left and went to the Parliament House, known as the White House. When they got there, they tried to break down the doors.
This is why the police reaction started. Police said that they do not interfere with peaceful protests until – but this was seen as a provocative act.
The two leading parties, each receiving a quarter of the vote, were Birimdik and Meknim Kyrgyzstan.
Asylbek Jinbekov, the younger brother of President Jinbekov, is a member of Birimdik.
Meknem Kyrgyzstan, meanwhile, is believed to be closely associated with the powerful Matrymov family. The family’s figurehead, Ryambek Matreimov, was the target of anti-corruption protests last year and is believed to have helped fund Mr Jinbekov’s successful 2017 presidential campaign.
Late Monday, Birimdic announced it would be open to re-run in Sunday’s election, and also invited other parties who have crossed the 7% threshold.