Northern Ireland wants to move away from “them-and-us” politics, the leader of the Greens said after her party made significant gains in the local elections. The party won four seats on Belfast city council, including holding one gained in 2014. The centrist Alliance party also made gains in Belfast, going from eight to 10 seats.

The Green party leader, Clare Bailey, said she felt “overwhelmed” by the success. “People have really come out and supported us, they have shown us by their vote that they really want to make the change and our conversations at the door have really resonated; climate change and climate chaos right at the front of the arguments,” she said.

“So regardless of our traditional cultural identities, the them-and-us politics, what we really need to be looking at is how we all mitigate against climate change, and that message is just being understood on the doors and over the last few days we are seeing that result coming in. It’s phenomenal.”

With all first preference votes now counted, the Alliance and Green parties, along with other small parties and independents, showed clear gains.

The Alliance, a cross-community party that is the minnow of the five main Stormont parties, more than doubled its 2014 showing by achieving 11.5%, boosting its presence on councils across Northern Ireland.

People Before Profit, a left-wing group, won 1.4%, four times more than its previous share, winning seats for brothers Matt and Michael Collins, who will represent the party on Belfast city council, and a seat for veteran social justice campaigner Eamonn McCann, who will sit on Derry City and Strabane district council.

In a region of calcified politics where big parties fight elections on constitutional lines to rally voters to green or orange banners, the results showed some people now wanted change.

“If you look across the board this election has been about progressive politics,” Naomi Long, the Alliance leader, told the BBC. “The public were sending a message: we want to move forward.” The two main parties should heed this message, she said.

The result was especially welcome for the DUP, which defied predictions of a backlash over its role in a so-called cash-for-ash scandal and its support for Brexit. DUP leaders also celebrated the victory of Alison Bennington, the party’s first openly gay candidate, who won a seat in Antrim and Newtownabbey despite protests from socially conservative colleagues. The result will embolden DUP modernisers.

Full results will be announced on Sunday, revealing how vote shares have translated into council seats.

Rival unionist parties were the main losers. The Ulster Unionist party (UUP), once Northern Ireland’s political colossus, continued to decline, dwindling from 16.1% in 2014 to 14.1%. The party that dominated Belfast City Hall for decades has been reduced to just two councillors, dropping from seven in 2014. Traditional Unionist Voice lost about half its share, tumbling to 2.2%. The Progressive Unionist party, Ukip and the Conservatives also lost ground.

Sinn Féin had hoped to further marginalise its nationalist rival, the SDLP, which has suffered a series of setbacks. But the smaller party’s first preference share dropped only slightly to 12%, showing unexpected resilience, while Sinn Féin struggled to make ground in several middle-class districts.