Kyrgyz security forces stopped several busloads of supporters of regional leader Urmat Baryktabasov on the outskirts of the capital Bishkek.
After a stand-off lasting several hours, they fired tear gas and blank rounds to disperse the crowd, who were traveling to the capital from Baryktabasov's home town.
Around 2,000 to 3,000 other demonstrators, meanwhile, massed in the capital to demand a role in the government for Baryktabasov, who recently returned from exile after a failed attempt to seize power five years ago.
Kyrgyzstan, a poor mainly Muslim former Soviet republic, has been in turmoil since a popular uprising toppled its president Kurmanbek Bakiyev in April.
An interim government has struggled to impose its authority since, amid savage fighting between ethnic groups which killed over 350 people and left thousands homeless.
Renewed violence, particularly in the north of Kyrgyzstan — which hosts US and Russian military air bases and escaped the bloodshed that engulfed the south in June — could disrupt the interim government's plan for elections in October.
Keneshbek Dushebayev, head of the Kyrgyz National Security Service, told Reuters the army was acting on information that some of those arriving by bus from the shores of Lake Issyk-Kul were armed and could try to overthrow the interim government.
"If their demands are not met, they are intent on seizing power," he said in the village of Kirshyolk, where helicopters roared overhead and 500 troops gathered to block the road.
Baryktabasov tried to seize power before the presidential election in 2005 that swept Bakiyev into office. Bakiyev was deposed in a popular revolt in April, during which 85 people were killed after troops opened fire on crowds protesting against corruption and poverty.
After his failed 2005 coup, Baryktabasov fled the country but returned after the overthrow of Bakiyev. A Reuters photographer at the scene said Baryktabasov had appeared among the crowd of his supporters at the roadblock.
People in the crowd whistled, waved red flags and shouted their demands to be admitted to Bishkek to attend the rally. They made no explicit demands beyond being allowed through the military cordon, and dispersed after the tear gas was fired.
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Some diplomats say acting President Roza Otunbayeva, a former ambassador to Britain and the United States, faces an uphill struggle fostering democracy in impoverished Kyrgyzstan, where the economy is expected to shrink by 5 percent this year.
In central Bishkek, a crowd of between 2,000 and 3,000 demonstrators held banners saying: 'Hands Off Baryktabasov!' Some demanded that he be allowed to speak on the makeshift stage erected outside the parliament building.
"We live in poverty. In the south, there are also many who are against those in power," said Avazbek Abakirov, a man in his mid-forties in the crowd outside the parliament building. "The population wants to unite around Baryktabasov."
But Farid Niyazov, spokesman for the interim government, said Baryktabasov was ineligible to participate in the elections because he was a citizen of neighboring Kazakhstan.
The crowd outside parliament later began to disperse peacefully.
Dushebayev said the crowd at the roadblock had arrived from Balykchy, a town on the western edge of Lake Issyk-Kul, and that some had demanded a place for Baryktabasov in the government. There appeared to be no inter-ethnic element to the stand-off.
"We received information that some of these people are armed with firearms and grenades," the security chief said.
In a statement, the Interior Ministry said the situation in Bishkek was under control and that criminal groups were responsible for the latest unrest.
