BAGHDAD (AP) — At least three anti-government protesters have been killed in clashes with security forces in southern Iraq, officials said Tuesday, as authorities tried to reopen the country's main port, which had been blocked by demonstrators for three days.

Security and medical officials said a protester was killed and eight more were wounded in Umm Qasr, a key oil terminal on the Persian Gulf. The Iraqi High Commission for Human Rights, a semi-official agency, said two people were killed and 23 wounded in clashes in the southern city of Nasiriyah.

The officials, who spoke on condition of anonymity because they were not authorized to talk to reporters, said security forces in Umm Qasr fired live ammunition and tear gas, and that protesters seized an armored vehicle.

Security forces in Iraq have killed at least 267 protesters in two major waves of anti-government demonstrations since Oct. 1 in Baghdad and across the mostly Shiite south. The protesters want an overhaul of the political system established after the 2003 U.S.-led invasion, accusing the government and major parties of corruption and incompetence in dealing with the economy and unemployment.

In southern Iraq, protesters have ransacked and torched the offices of political parties linked to Iran. On Sunday night, they attacked the Iranian Consulate in the Shiite holy city of Karbala.

In Baghdad, protesters crossed a Tigris River bridge on Monday and clashed with security forces near the headquarters of state-run TV and the office of Prime Minister Adel Abdul-Mahdi. At least five protesters and a member of the security forces were killed, and scores were wounded. The protesters set tires and trash containers ablaze within 500 meters (yards) of the offices, sending huge clouds of black smoke into the sky.

Netblocks, a group that monitors worldwide internet access, reported a major shutdown by Iraqi authorities overnight, with usage in Baghdad and southern Iraq dropping to 19% of normal. It said the internet was partially restored early Tuesday, but that "some networks are still offline and social media and messaging apps remain blocked or degraded."

Authorities shut down internet access and blocked social media sites several times during the protests in October, but Netblocks said the latest shutdown was the most severe yet.

Abdul-Mahdi has expressed support for the protesters' demands and condemned violence on all sides while resisting calls to step down. He has urged protesters to reopen roads so that life can return to normal, saying the disruptions are costing billions of dollars.

He met with senior judicial and security officials at the Federal Police Headquarters late Monday to discuss how to restore stability while preserving the right to protest and to protect private property, a government statement said.

The British Embassy urged Iraq's government to ensure security forces "protect protesters and act appropriately." It said on its Facebook page: "Peaceful protest is the right of the Iraqi people. Violence against them is unacceptable."

U.S. Secretary of State Mike Pompeo said last week that Iraq's government should listen to the protesters' "legitimate demands."

Iraqi politics are dominated by Shiite Islamist parties, many with close ties to Iran. The protesters, who mainly come from the Shiite majority, say their leaders have enriched themselves while letting the economy and public services deteriorate.

Despite Iraq having the world's fourth-largest proven oil reserves, Baghdad and other cities still suffer frequent power cuts and the tap water in many areas is undrinkable.

Associated Press writer Joseph Krauss in Beirut contributed.