State television in Uzbekistan says a suicide bomber has killed a police officer and wounded several people in the eastern city of Andijan.
It said that earlier up to three men used guns and explosives to attack a police checkpoint at nearby Khanabad.
The reports said another officer and a gunman were injured, and that the attackers managed to escape.
They are said to have come from Kyrgyzstan. The two countries closed their border after the first attack.
The motive for the attacks is not clear, but Uzbek media have speculated about a possible failed terrorist operation.
Security services and military reinforcements have been sent to Khanabad.
The Ferghana Valley, where Khanabad is located, has been the scene of several attacks by militant groups in the past.
Observers say the rule of President Islam Karimov has fuelled extremism in the region.
Local people in Andijan say that security forces shot dead hundreds of mainly peaceful protesters in 2005.
The violence there broke out after an armed jailbreak turned into a huge demonstration involving thousands of Uzbeks.
The Uzbek government has denied there was a massacre of civilians, saying it thwarted an Islamist uprising.
It says the death toll was exaggerated, and that nearly all of those who died were soldiers or terrorists.