Iraqi security forces shot dead at least six anti-government protesters in Baghdad on Thursday and killed four others as they broke up a sit-in in the southern city of Basra, police and medical sources said. Scores more were wounded in the clashes as weeks of deadly violence in Iraq over protests against an entrenched political elite showed no signs of abating. Security forces used live fire against protesters near Shuhada Bridge in central Baghdad. Gunfire was used against demonstrators in Basra, the main source of Iraq's oil wealth, who had staged a days-long sit-in. Earlier on Thursday the Iraqi army ordered security forces to "immediately arrest" any people causing chaos on the roads as transport routes were cut by anti-government protesters. Iraq has been gripped by protests in the capital Baghdad and across most of its southern provinces by demonstrators calling for the removal of a political class they view as corrupt and beholden to foreign interests, including Iran and US. Gen Abdul Karim Khalaf, army spokesman, said security forces would "arrest anyone trying to block roads or bridges" and urged the protesters to avoid violence. More than 260 protesters have been killed in a brutal crackdown by security forces since the protests began on October 1, including four in the capital on Thursday. Gen Khalaf said that no live ammunition was being used. "To avoid any confusion, clear and strict instructions have been handed down that no live ammunition be used," he said. "Orders have also been given not to allow any live ammunition at the scene of protests." UN Secretary General Antonio Guterres expressed "serious concern" over the rising death toll and injuries. "Reports of the continued use of live ammunition against demonstrators are disturbing," Mr Guterres said on Wednesday. He called for all acts of violence to be investigated "seriously" and renewed his appeal for "meaningful dialogue between the government and demonstrators". The protests in Baghdad have been concentrated in Tahrir Square but have spilled over to four main bridges leading from the area. On Thursday, security forces shot dead at least four protesters and injured 35 during clashes near the Shuhada Bridge, police said. In the south, demonstrators have staged sit-ins blocking main roads and state infrastructure, including oilfields, in Opec's second-biggest producer. Protesters burned tyres and blocked the entrance to the port of Umm Qasr, preventing lorries from delivering vital food imports, hours after operations had resumed, port officials said. The port receives most of the grain, vegetable oils and sugar imported into Iraq. The UN envoy to Iraq, Jeanine Hennis-Plasschaert, expressed "grave concern" over the disruptions, which she said were costing Iraq billions. "It is detrimental to Iraq’s economy and undermines fulfilling protesters’ legitimate demands," Mrs Hennis-Plasschaert said on Twitter. Her comments were widely rejected on social media, especially by Iraqi protesters who have so far been unmoved by pleas to go home, pledges of reform or talks to produce a solution to the crisis. The government says it is enacting reforms but has offered nothing that is likely to satisfy most protesters. Despite Iraq's vast oil wealth, one in five people lives in poverty and youth unemployment stands at 25 per cent, the World Bank says.