Thunberg, meanwhile, was on a boat sailing across the Atlantic, but tweeted a photo of herself holding a sign that said "School strike for climate".
Climate activists around the world are taking to the streets in the fourth global climate strike today.
The latest demonstrations come as 200 nations prepare to gather in Madrid next week for a 12-day UN climate conference.
Protesters in Paris also formed a human chain at La Defense shopping mall that prevented people from reaching stores, to highlight the climate costs of consumerism. They were joined by victims of the bushfires that have been ravaging parts of the country.
Thunberg is due to speak in the Portuguese parliament on arrival in Lisbon before going on to Madrid.
In Montreal, environmental groups distributed second-hand clothing.
"We are trying to create an eco-responsible movement against mass consumption, so we are giving away clothes for free to encourage people to consume less", protester Germain Desloges told AFP.
Schoolchildren were among the protesters who congregated outside the headquarters of Australia's ruling party in Sydney on Friday at the start of a new round of global protests against climate change under the "Fridays for Future" banner.
Holding home-made signs, including "The climate is changing, why aren't we?", protesters in Sydney accused the government of inadequate action in addressing Australia's bushfire crisis.
Protests also took place in Tokyo, where hundreds marched through the teeming Shinjuku district to raise awareness of the issue.
"I feel a sense of crisis because nearly no one in Japan is interested" in climate change, 19-year-old student Mio Ishida said.
"I was really inspired by Greta's actions", she said. We have to ask: "How far does this have to go before our government finally takes action?" New Delhi is one of the world's most polluted cities.
The meeting will focus largely on finalizing the "rulebook" for the 2015 Paris climate treaty, which becomes operational in 2021.
Scientists have warned that efforts to cap warming to 1.5 Celsius are failing and that carbon emissions - which are on the rise - would need to fall 7.6 percent a year to meet the target.
It comes as experts have warned that global temperatures could rise sharply this century with destructive consequences after greenhouse gas emissions hit record levels.