Kyrgyzstan said Friday that three citizens were killed after Uzbek troops opened fire at the disputed frontier of the two Central Asian countries.

Border disagreements have dogged the republics formerly controlled by Russia throughout their three-decade independence, with decision-makers referring to different Soviet-era maps to back up their territorial claims.

"Without regaining consciousness, they died from their gunshot wounds," the Kyrgyz national security committee said in a statement, adding that it had taken place on Thursday.

It was the most serious incident to occur at Kyrgyzstan and Uzbekistan's frontier in recent years.

The statement said representatives of both the border services had made contact immediately and agreed to conduct an investigation.

They were due to meet on Friday, it added.

Kyrgyzstan did not say whether the dead were civilians or border troops.

Smuggling is a common problem in the region while border communities also clash regularly over land for grazing animals and water resources.

Uzbekistan's border service could not be reached for comment.

Bilateral relations between the neighbours had been poor but improved markedly after the death of long-ruling hardline Uzbek president Islam Karimov in 2016.

Karimov's successor, Shavkat Mirziyoyev, went about mending Tashkent's frayed ties with neighbours.

Uzbekistan and Kyrgyzstan last year signed an agreement to resolve the border dispute, but the deal was not ratified after Kyrgyz citizens voiced dissatisfaction over terms that guaranteed the Uzbek side use of a reservoir located in Kyrgyzstan.

The most explosive conflict in Central Asia at present is at Kyrgyzstan's border with Tajikistan, where several dozen people were killed following unprecedented clashes involving military units last year.