Uzbekistan's president on Sunday announced fatalities among civilians and law enforcement personnel during protests in the country's autonomous Karakalpakstan region, which has seen massive unrest over a planned constitutional reform.

"Unfortunately, there are fatalities among civilians and law enforcement officers," Shavkat Mirziyoyev said Sunday during a speech in Karakalpakstan that was relayed by his press service on Telegram.

He did not give any specific number or detail the cause of death.

Uzbekistan on Saturday decreed a month-long state of emergency in the impoverished western region where a large protest erupted Friday over proposed changes to the constitution that would have weakened the region's status.

Mirziyoyev has since pledged to withdraw the amendments affecting the region from the draft constitution, which is expected to go to a referendum in the coming months.

The clashes pose the most significant challenge yet to the 64-year-old's rule since he rose to power from the post of prime minister in 2016 when long-serving mentor Islam Karimov died.

On Sunday, Mirziyoyev made his second visit to Karakalpakstan in two days and accused protest organisers of "hiding behind false slogans" and trying to "seize the buildings of local government bodies" in an address to local lawmakers.

"Several groups attempted to seize the buildings of the Nukus City Department of Internal Affairs and the Department of the National Guard in order to obtain weapons," he claimed.

'Shameless provocations'

"Taking advantage of their numerical superiority, these men attacked law enforcement officers, severely beating them and inflicting severe injuries," he added.

Videos that appear to show people dead and injured from the clashes have raised concerns that the security crackdown has caused a high death toll.

Uzbek lawmaker Bobur Bekmurodov complained of "shameless provocations" as internet users shared footage of men in uniform moving through a street covered in red liquid on Twitter.

"Dear friends, please do not become part of this shameless provocation. Check the information. It is just red colour water. Please, share the truth!" he tweeted.

Police said Saturday they had detained "organisers of riots" but did not provide figures.

Karakalpakstan has seen significant internet outages since the draft amendments were published last week, stripping the region of its nominal "sovereign" status and its right to secede from Uzbekistan via popular referendum.

Mirziyoyev's press service said Saturday night that he had pledged articles of the constitution concerning the region would remain unchanged "on the basis of... the opinions stated by residents of Karakalpakstan" during his meetings with local authorities.

Residents of the region told AFP that they have received SMS notifications that the amendments were cancelled.

The autonomous republic's constitutional right to break away from Uzbekistan is a legacy of an agreement struck between Karakalpakstan and the central government in Tashkent after the collapse of the Soviet Union. The authoritarian government has never appeared willing to entertain the prospect.

One amendment set to remain in the draft document will allow presidents to run for seven-year terms, directly benefitting Mirziyoyev, who crushed token opponents to secure a second five-year term in October.

Karakalpakstan takes its name from the Karakalpak people. The minority is well represented in cities such as Nukus, where the protest took place, but now constitute a minority in the western region of two million people.

The size of the protest on Friday was unprecedented for the region and possibly Uzbekistan, which saw over 170 people killed during unrest in 2005 in the city of Andijan according to an official toll considered on the low side at the time.

Two Nukus eyewitnesses speaking on condition of anonymity confirmed to AFP that a smaller group of protesters had gathered close to a city market on Saturday night before police broke up the demonstration using what appeared to be tear gas and smoke grenades.

Eyewitnesses said Nukus was quiet on Sunday morning, with police and military patrolling the streets.

Karakalpakstan is closely associated with the drying of the Aral Sea -- one of the world's great man-made environmental catastrophes.

Once the world's fourth-largest lake, the Aral shrank massively due to Soviet agricultural policies that saw rivers that fed into it diverted, largely to expand cotton production.