A general strike and tens of thousands of protesters have brought the southern Tunisian city of Gabes to a standstill as anger intensifies over a state-run chemical plant that residents blame for a pollution crisis.

Shops, markets, schools, and cafes shut down in the general strike, halting economic activity in coastal Gabes on Tuesday in response to a call by the powerful UGTT labour union.

Crowds held up banners condemning the environmental pollution that has been caused by the CGT phosphate plant for years and that critics say now threatens the health of thousands of residents.

Protesters marched through the city chanting slogans such as “Gabes wants to live” and “dismantle the polluting units”.

“Everything is closed in Gabes,” said Saoussen Nouisser, the local representative of UGTT. “We’re all angry at the catastrophic environmental situation in our marginalised city.”

Gabes, home to nearly 400,000 people, has seen thousands take to the streets in recent weeks, demanding the immediate shutdown of the plant.

The unrest has grown into one of the biggest tests facing President Kais Saied since he seized extraordinary powers in 2021.

Saied has described the situation as an “environmental assassination” while blaming past administrations for widespread cancer and respiratory illness and the destruction of local ecosystems.

Sami Al-Tahiri, the UGTT secretary-general, told local media that the strike had “succeeded across all segments of the population”, adding that Tunisians were “prepared to struggle for their legitimate demands” and hold authorities accountable for failures across social, economic, and environmental fronts.

He said the union was ready to escalate with further protests and mass rallies.

Residents say the plant, opened in 1972 to produce fertilisers, is responsible for a surge in gas poisoning, cancer cases and collapsing marine life, as radioactive waste and phosphogypsum are released into the sea and open air.

More than 200 people have been admitted to hospital in recent weeks for respiratory distress and exposure to gas, according to medical sources and NGOs.

“The plant has poisoned everything – the trees, the sea, the people,” local environmental activist Safouan Kbibieh told Reuters. “Even Gabes’s pomegranates now taste like smoke.”

Despite a 2017 government pledge to phase out the plant, authorities this year instead moved to boost production, calling phosphate a “pillar of the national economy”.

Authorities have said “urgent measures” are under way and have brought in Chinese companies to help contain gas emissions and prevent further dumping into the Mediterranean.