Yerevan (AFP) - Gayane wept with joy as she watched four doves fly into the leaden sky over Yerevan, where tens of thousands of people poured onto the streets to celebrate opposition leader Nikol Pashinyan's election as prime minister on Tuesday.

"I am so happy!" the 29-year-old sobbed as warm rain fell on the crowds. "I was waiting for this moment for so long. Pashinyan will change everything in Armenia."

Earlier on Tuesday Armenia's parliament elected the 42-year-old opposition leader as prime minister after he spearheaded weeks of mass protests against the ruling party, transforming the country's political landscape.

Yerevan's central Republic Square quickly filled with a sea of Armenia's red-blue-and-orange national flags and a huge crowd sang the national anthem and chanted "Armenia! Armenia!"

"From now on, nobody will violate the Armenian people's rights and freedom!" Pashinyan told the crowd.

The father of four is often seen as a man of the people, a reputation backed up by the trademark camouflage T-shirt he wore during protests.

But on Tuesday, the newly elected premier swapped his street attire for a sleek suit, transforming himself into a polished politician with a bashful smile.

The honking of car and vuvuzela horns mingled with shouts of joy as groups of young people danced folk dances to beating drums.

"What a great feel of freedom!" said 42-year-old economist Ruzanna Sargsyan. "The people now believes in its strength, that change can be achieved."

Her friend Gohar Harutyunyan, a 39-year-old financier, said: "Armenia now believes in a better future. ... Armenia has every reason to celebrate. This is a great, historic day."

"What I like about Pashinyan is his style," said Karen, 25, who had tied a ribbon in the colours of Armenian flag around the neck of his dog, Zeus.

In a nearby street, an ancient Soviet car and a glittering BMW together blocked traffic, their owners playing music at a deafening volume.

For 28-year-old Minas Sarkisian, the most important thing is Pashinyan's promise to fight endemic corruption and boost the economy in the impoverished Caucasus nation of 2.9 million.

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"I'm a cook in a Mexican restaurant, but I also work as a waiter to make ends meet," said Sarkisian, who earns "between $400 and $500 a month."

"It's not enough to live on, and I can never go on holiday," he said, expressing confidence that Pashinyan will "transform the economy" in the country where more than 30 percent of people live below the poverty line according to official statistics.

But some were more cautious.

"I don't want to delude myself too much," said 27-year-old Hayk.

"I'm not pessimistic, but I think people should rely more on themselves to change their own lives."