MARIUPOL, Ukraine — Steelworkers from plants owned by Ukraine’s richest man retook government buildings from pro-Moscow insurgents, reversing the tide of rebellion and lawlessness that has gripped this industrial port and dealing a setback to anti-Kiev forces aspiring to merge with Russia.

Wearing overalls and hard hats, dozens of workers cleared away barricades of debris and tires outside the Mariupol city hall Friday, scoring early successes against the pro-Russian forces, but threatening to open a new and dangerously unpredictable cycle of confrontation.

“People are tired of war and chaos. Burglaries and marauding have to stop,” said Viktor Gusak, a steelworker who joined in the effort to banish the pro-Russia militants from Mariupol, the Donetsk region’s second-largest city and the site of bloody clashes last week between Ukrainian troops and the insurgents.

‘PEOPLE’S REPUBLICS’

About 75 miles to the north, armed backers of Ukrainian unity dressed in black seized control of a police station in a village just inside the troubled Donetsk region, vowing to expel the separatists through force if necessary.

The moves, which began Thursday in Mariupol and the village of Velyka Novosilka, were a blow to the separatists who have seized control of government offices in this city and a dozen others in the east.

Other similar and apparently unaccountable groups look to be emerging elsewhere in the chaotic east.

Should they make substantial incursions, it is unclear whether they will be perceived as liberators or attackers acting on behalf of a little-liked government in Kiev. The latter could precipitate civil conflict.

Government forces have in recent weeks achieved only limited results in quashing the self-styled Donetsk and Luhansk “people’s republics” — armed groups that this week declared independence for their regions following contentious referendums.

Polls have shown, however, that a majority of eastern Ukrainians support unity, though most are too fearful of the pro-Russian militias to say so publicly.

CITIZEN PATROLS

That has handed the initiative to expel the insurgents to forces acting independently of authorities in Kiev.

In Mariupol, billionaire Rinat Akhmetov’s Metinvest holding group organized citizen patrols of steelworkers working alongside police to help improve security and get insurgents to vacate the buildings they had seized.

Until now, Akhmetov had been notable for his noncommittal stance during the turbulence that has for more than a month gripped the region that is home to his most lucrative industrial assets.

A video statement by the 47-year-old industrialist Thursday called for major constitutional reforms, while preserving a united Ukraine.