Tens of thousands of people marched through the centre of the Armenian capital Yerevan on Thursday, protesting against a government decision to cede land to arch-foe Azerbaijan.

Armenia has agreed to hand over territory it has controlled since the 1990s and started border delimitation efforts in a bid to secure an elusive peace deal with Baku and avoid another bloody conflict.

The two South Caucasus nations have been locked in a stand-off over disputed territory, primarily Nagorno-Karabakh, since the break-up of the Soviet Union.

"I came here today because I want to leave our children a beautiful country ... We can't go on like this, always giving away our land," Edik Nikoghosyan, 77, told AFP at the protest.

Demonstrators began marching to the capital following protests six days ago in Armenia's northeastern Tavush region where the government has agreed to hand over some territory.

Members of opposition parties and organizations representing refugees from Nagorno-Karabakh joined tens of thousands outside the government building on Yerevan's Republic Square.

Azerbaijan seized Nagorno-Karabakh in a lightning offensive last year, causing almost the entire local population of more than 100,000 ethnic Armenians to flee.

Prime Minister Nikol Pashinyan has since agreed to cede control of four Azerbaijani villages in the Tavush region that Armenia's forces took in the 1990s.

He said this would be the first step towards securing a peace deal with Baku and that Yerevan would not hand over any of its "sovereign" territory.

But the concessions have sparked weeks of protests by people who have blocked major roads in a bid to force Pashinyan to change course.

"Nikol (Pashinyan) is busy trading our land, making money. As soon as possible we must remove him from office," said Norik Shahramanyan, a 70-year-old protestor.

"I fought for Artsakh until the end, but we lost it," said Tigran Balasanyan, 43, using the separatist Armenian name for Nagorno-Karabakh, which is internationally recognized as part of Azerbaijan.

"I don't want to lose Armenia as well. We must not allow weak authorities to give away Armenia," he said.