Tens of thousands of supporters of Armenia's protest leader, Nikol Pashinyan, have responded to his call for civil disobedience, blocking key roads and government buildings.
He has led weeks of anti-government protests that forced Serzh Sargsyan to resign after 10 years in power.
Mr Pashinyan called for a general strike after ruling party MPs refused to back him as interim prime minister.
Protests broke out across the capital Yerevan and other main cities.
Cars and lorries blocked intersections in the capital, while demonstrators stopped traffic on the route to the main airport. Tourists had to abandon vehicles and carry their luggage. Metro stations in Yerevan were closed as part of the campaign of disobedience.
Thousands already in the #republic sq in #YerevanNow after a day of nationwide general strike. #Armenia people make it clear in any possible way that they want this man #Pashinyan to be their PM pic.twitter.com/GypLMOvmZt— rayhan demytrie (@rayhandemytrie) May 2, 2018
Teachers and school students were among those taking part in the protests in the landlocked former Soviet state of 2.9 million people, a close ally of Russia. The southern Caucasus country shares borders with Turkey, Georgia, Iran and Azerbaijan.
How did we get here?
Mr Sargsyan left the presidency last month after 10 years in power and was then elected prime minister by a parliament controlled by his Republican party. Under a 2015 referendum marred by irregularities, Armenia shifted powers from the president to parliament.
Mr Sargsyan's move was seen by critics as a way of clinging to office.
Demonstrators poured on to the streets of Yerevan after Mr Pashinyan addressed crowds on Tuesday night in Republic Square, close to parliament.
He told the BBC on Wednesday that protesters were fighting for their rights and dignity. "I want to be clear, it isn't a fight for Nikol Pashinyan becoming prime minister, it's a fight for human rights, for democracy, for rule of law and that is why our people aren't tired and won't be tired."
The acting head of government, Karen Karapetyan, has called for talks to end the crisis.
"A prime minister should only be elected in parliament according to the constitution," he said.
'No longer afraid'
By Rayhan Demytrie in Yerevan
Yerevan's Republic Square is packed again. Thousands of Armenians from different corners of the country have come here to show their support for Nikol Pashinyan.
His face is printed on T-shirts, flags and posters. Sara Akopyan is wearing such a shirt; she is in the square with her colleagues from a real estate agency. "It's a general strike today and we are not working, this strike is by far the biggest one that swept Armenia," she says.
Her friends say they are ready to miss work for however long it takes, because this time around there is no turning back for Armenians.
"We are doing this for our future, we want to live in a country ruled by law and not by a gang."
They are saying that Armenians are united in their desire to move forward, and right now it's 55 people against the whole nation, a reference to the MPs from the Republican Party that rejected Nikol Pashinyan's bid for premiership on Tuesday.
One lady I interviewed today, from the Sevan region, said she was no longer afraid to talk openly about the problems in the country.
Where has been affected?
Entrances to several ministry buildings in Yerevan were blockaded and rail services were disrupted. Trains were not running between Yerevan and the second city, Gyumri, and checkpoints near the Georgian border were affected.
There was further disruption in Gyumri itself and in the third city Vanadzor, where a large crowd of protesters blockaded the mayor's office and other civic buildings. Three thousand workers from a local sewing factory walked out and cut off some of Vanadzor's biggest roads, reports said.
During the day Mr Pashinyan posted a message on social media, urging protesters to halt disruption at the airport, while other opposition politicians appealed to people not to impede emergency services. Police tried to move protesters off the roads but there was no sign of violence.
In his Tuesday speech, Mr Pashinyan had called on police to join the protests.
What happens next?
Parliament is expected to try again to elect a prime minister on 8 May.
There are concerns that a lack of stability in Armenia could cause disruption in the wider region. The country has a decades-long territorial dispute, which has produced periods of conflict, with Azerbaijan over the Nagorno-Karabakh region.
Russia has been strongly aligned with Armenia since the Soviet era and has military bases in the county. However, Mr Pashinyan has promised that the two countries will remain strategic allies if he comes to power, according to Russian agency Tass.
The leader has also told supporters he has received reassurance from Moscow that "Russia would not intervene in Armenia's internal affairs".
Who is Nikol Pashinyan?
The son of a sports teacher, Mr Pashinyan came to prominence in 1995 when he began writing about government corruption. He founded a newspaper three years later and went on to take the role of editor at a best-selling daily, which criticised the government of President Robert Kocharyan and then of President Sargsyan.
When Mr Sargsyan was elected president in 2008, Mr Pashinyan was among the leaders of protests that turned violent and left 10 people dead. At that point he went into hiding, surrendering to authorities the following year.
Jailed the following year on charges of murder and organising mass unrest, he was eventually released under an amnesty in 2011.
In 2012, he was first elected to Armenia's parliament. He argues that only he can steer Armenia to free and fair elections.
His critics accuse him of bringing chaos to the streets and question his ability to lead as prime minister.
What was the tipping point?
Mr Pashinyan fell eight votes short of the 53 he needed to secure a majority in the 105-seat chamber on Tuesday, when he failed to persuade the ruling Republican party to back him.
During a marathon nine-hour question-and-answer session, he warned MPs what would happen if they rejected his candidacy. "Your behaviour, treating the tolerance of the people as a weakness, could become the cause of a tsunami."
Republican MPs had reportedly given assurances they would not block Mr Pashinyan's bid for office and did not put up their own candidate in a bid to ease tensions.
However, some still questioned his leadership qualities.
"Mr Pashinyan, I don't see you at the post of prime minister, I don't see you at the post of commander-in-chief," said Eduard Sharmazanov, deputy speaker of parliament and Republican spokesman.
Mr Pashinyan's supporters shouted "shame" when the result of the parliamentary vote was shown on two huge screens in Republic Square.
The opposition leader, accompanied by his wife, arrived in the square soon after, with the crowd chanting "Nikol, Nikol".