* More than 260 killed since protests began
* Security forces use live fire and tear gas
* Protesters blockade major port
BAGHDAD, Nov 7 (Reuters) - Iraqi security forces shot dead at least six anti-government protesters in Baghdad on Thursday, police and medical sources said, as weeks of deadly unrest showed no signs of abating.
Another 38 people were wounded in the clashes near the Shuhada Bridge, they said, as mass demonstrations continued for a 13th straight day with thousands thronging central areas of the capital.
In southern Iraq, dozens of protesters burned tyres and blocked the entrance to the port of Umm Qasr, preventing lorries from transporting food imports, just hours after operations had resumed, port officials said.
Security forces used live fire and tear gas to disperse protesters who gathered at a local government building on Thursday afternoon, police sources said.
The Iraqi government has failed to find a way out of the biggest and most complicated challenge it has faced in years. The unrest has shattered the relative calm that followed the defeat of Islamic State in 2017.
A crackdown by authorities against mostly unarmed protesters has killed more than 260 people since unrest broke out on Oct. 1 over lack of jobs, poor prospects and corruption.
Protesters, mostly unemployed youths, blame a political elite that has ruled Iraq since the toppling of Saddam Hussein in 2003, and demand a complete overhaul of the political system.
The country is beginning to feel the pinch of the unrest, which started in Baghdad and spread to southern cities.
Meanwhile, internet outages imposed by the government to try to stem unrest have hit the private sector, a central bank source said.
The source said private banks in Iraq had recorded losses of some $16 million per day since the internet was first shut down at the beginning of October.
FISCAL PINCH FELT
Combined losses by the private banks and mobile phone companies, money transfer services, tourism and airline booking offices had averaged more than $40 million per day, the source said - almost $1.5 billion for Iraq in just over a month.
Umm Qasr briefly resumed operations early on Thursday after most protesters cleared the area. But several dozen activists, relatives of a demonstrator killed during weeks of violence, then returned to block the main gate, port officials said.
Umm Qasr receives most of the grain, vegetable oils and sugar that Iraq depends upon.
Oil and security officials said operations resumed on Thursday at the nearby Nassiriya oil refinery, where protesters had stopped fuel tankers entering or leaving the day before.
Oil production and exports have not been significantly affected by the unrest, oil ministry officials say.
But the halting of fuel tankers that transport fuel from the Nassiriya refinery to regional gas stations caused fuel shortages across the southern Iraqi province of Dhi Qar. The refinery had recently been producing around half its capacity, oil officials said.
The internet returned briefly in most parts of Iraq on Thursday but went out again after 1:00 p.m. local time (1000 GMT). Authorities have heavily restricted internet access during the protests.
The government says it is enacting reforms but has offered nothing that is likely to satisfy most protesters.
Stipends for the poor, more job opportunities for graduates and pledges to punish a handful of corrupt officials have come too late for those demanding an overhaul of state institutions, a flawed electoral process and system of governance that has fuelled endemic corruption, many Iraqis say. (Reporting by Baghdad newsroom, Aref Mohammed in Basra Writing by John Davison Editing by Angus MacSwan, Peter Graff and Giles Elgood)
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