At least seven people have been killed and dozens wounded in clashes across Iraq, as security forces fired live ammunition and teargas for the second day to disperse anti-government protesters demanding jobs, improved services and an end to corruption.

The deaths brought the overall number of protesters killed in two days of violence to nine. Protests on Tuesday had left two dead – one in Baghdad and another in the city of Nasiriyah – and over 200 wounded.

The renewed clashes occurred despite a massive security operation mounted by the government in an effort to quash the economically driven protests.

Iraqi security forces use a water cannon during a protest in Baghdad on Wednesday. Photograph: Hadi Mizban/AP

Hundreds of heavily armed security forces and riot police deployed on Baghdad streets blocked all intersections leading to a major central square on Wednesday to prevent a repeat of Tuesday’s protests. Residents said authorities had shut down social media platforms such as Facebook, Twitter and WhatsApp.

Groups of protesters continued to take to the streets, some of them calling for the government to be overthrown. Thick black smoke hung over the city as demonstrators set fire to tyres and garbage containers. Bursts of heavy gunfire could be heard intermittently.

The confrontations spread to at least seven other provinces in the country, with an estimated 3,000 protesters taking to the streets in the southern city of Basra. Late on Wednesday, a curfew was imposed in the southern cities of Nasiriya, Amara and Hilla.

The violence was some of the worst between protesters and security forces in Iraq, signalling that the war-weary country could be facing a new round of political instability. Iraq has been caught in the middle of US-Iran tensions in the Middle East, putting an additional strain on the weak government in Baghdad that hosts thousands of US troops and powerful paramilitary forces allied with Iran.

The protests, organised on social media, started in Tahrir Square on Tuesday, initially provoked by economic woes. They began peacefully, calling for an end to corruption, improved basic services and more jobs. But they soon turned violent after security forces repelled demonstrators with water cannons, teargas and live ammunition.

Protesters responded by calling for the toppling of the government, throwing stones at security forces and setting tyres and rubbish bins on fire. At least two protesters were killed and more than 200 were wounded.

A few dozen protesters tried to reach Tahrir Square again on Wednesday morning but were met with scores of riot police who formed a human barrier and soldiers who blocked roads, sometimes with barbed wire. Security forces again fired teargas and live ammunition into the air to disperse the protesters, chasing them away, according to officials.

Saadoun Street, a major commercial thoroughfare leading to Tahrir Square, was deserted and all the shops and restaurants were closed. Smoke could be seen near Tahrir and intermittent gunfire could be heard, as well as ambulance sirens.

Anti-government protesters set a fire and block roads in Baghdad on Wednesday. Photograph: Hadi Mizban/AP

“They have transformed Tahrir Square into Tahrir barracks,” said Hussein Saleh, 24. “There are more security forces than there are protesters,” he added, standing with a small placard that read: “I am protesting to take my rights.”

The protests are the most serious challenge to Adel Abdul Mahdi’s nearly year-old government and prompted the prime minister to hold a national security emergency meeting on Wednesday. His office later said the meeting denounced the violence that accompanied the protests and said measures will be taken to protect citizens and public property and that the government will spare no effort to fulfil the demands of the protesters.

A bridge that leads from the square to Baghdad’s fortified Green Zone — home to government offices and foreign embassies — was closed.

The protests appear to be spontaneous and without political leadership, organised by people on social media in protest against corruption and a lack of basic services such as electricity and water.