Uzbekistan says 20 suspected militants have blown themselves up during a fierce gun battle with special forces in the capital, Tashkent.
Many of the roads out of Tashkent have been closed
Three police officers were also killed after police and troops surrounded a building, the interior ministry said.
After several hours of armed exchanges, there was an explosion inside the building, followed by silence.
On Sunday and Monday, 19 people were killed and 26 injured in bombs in Tashkent and the city of Bukhara.
Tuesday's siege took place in the north of Tashkent.
Witnesses said four armed militants entered a house, which was then surrounded by the security forces.
An interior ministry statement read out on television said 20 militants blew themselves up with home-made explosives after being surrounded. Three policemen were killed and five were injured.
At least five bodies were reported to be lying in the street.
"You just can't imagine how terrible it was," one resident, 76-year-old Lyudmila Petrovna, told Reuters.
"First the special forces turned up like a bolt from the blue, all wearing masks and armed to the teeth.
"Then we were hastily evacuated and - along with our relatives - heard explosions and the shooting."
The interior ministry said a number of different operations were taking place in parts of the city, but gave no details.
The authorities have blamed Islamic extremists for the attacks which are the bloodiest seen in the former Soviet republic for five years.
The violence began on Sunday evening with an explosion at a house used by alleged militants in Bukhara, the authorities said.
On Monday, two female suicide bombers blew themselves up at a busy shopping bazaar.
One Islamist group, accused by the hardline secularist government of President Islam Karimov of being behind the attacks, has denied any involvement.
London-based Hizb ut-Tahrir said it "does not engage in terrorism, violence or armed struggle".
There were reports of fresh attacks against police officers on Tuesday.
Close to where the armed siege took place, police stopped a car at a checkpoint. Two people inside the car are reported to have detonated explosive-laden belts, killing themselves and three police officers.
There were reports of a second suicide bombing at a separate police post not far away.
Police 'disliked and feared'
President Karimov has said that whoever was responsible for the attacks must have connections with a foreign organisation. He has ordered huge numbers of police onto the streets to curb the violence.
But the BBC's Monica Whitlock, in Tashkent, says this measure may have increased the violence.
All of the attacks seem to be directed at police targets and now there are lone officers dotted around Tashkent's streets, highly visible and vulnerable to attack, she says.
Our correspondent says the police are widely seen as the main instrument of government in Uzbekistan, and are very much disliked and feared in some circles.
Finger of blame
Hizb ut-Tahrir said the government would use the attacks as a justification for the oppression of Muslims.
The group, which is banned in all central Asian states, advocates the introduction of Muslim Sharia law.
Monday's attacks were the country's first suicide bombings
Another group under suspicion is the home-grown Islamic Movement of Uzbekistan (IMU).
The group initially aimed to overthrow Mr Karimov and replace his administration with a Muslim government, although in 2000 its objective changed to establishing a radical Islamist state across Central Asia.
The group's leader Tahir Yuldashev is accused of orchestrating a series of deadly bomb attacks in Tashkent in 1999, one of which nearly killed Mr Karimov.
However, Shahida Tulaganova of the BBC's Central Asia Service says the group, which fought alongside the Taleban during the Afghan conflict, is now in tatters with many of its leaders being held by the US in Guantanamo Bay, Cuba.