Rallies continued to rage in the southern Iraqi city of Basra on Wednesday a day after at least five demonstrators were killed while protesting against poor government services. Prime Minister Haidar al-Abadi has since ordered a probe in the violence. In a statement issued Wednesday, the UN special representative to Iraq, Jan Kubis, expressed "grave concern" over events in Basra. Kubis called for calm and urged authorities "to avoid using disproportionate, lethal force against the demonstrators, provide the necessary protection for the people of Basra, ensure human rights while protecting law and order, and investigate and hold accountable those responsible for the outbreak of the violence." Like other cities in the long-neglected south, Basra is plagued by electricity outages, unemployment and entrenched corruption. On Wednesday, Iraqi security forces sprayed tear gas and fired into the air to try to disperse thousands of protesters in the city, in some of the worst unrest in the region for months. Frustrations were once again focused on the provincial governorate building, where thousands of people gathered. The crowds were growing as stones were hurled at the building. Some protesters tried to break down concrete barriers around the governorate. An AFP journalist reported gunshots and tear gas were fired by security personnel as they faced off with several thousand demonstrators outside the building. The measures failed to disperse protesters, who responded by hurling Molotov cocktails and letting off fireworks at the security forces. Basra residents say salt seeping into the water supply has made it undrinkable and sent hundreds to hospital. This is proof, they say, that infrastructure has been allowed to collapse in the part of Iraq that produces most of its oil wealth. Public anger has grown at a time when politicians are struggling to form a new government after an inconclusive parliamentary election in May. Elections victor, cleric Moqtada al-Sadr said in a tweet ahead of the latest clashes that "vandals infiltrated" the protesters.