WASHINGTON/NAIROBI, Nov 5 (Reuters) - A newly-formed alliance of Ethiopian opposition factions set a goal on Friday of bringing down Prime Minister Abiy Ahmed by force or negotiation to then form a transitional government. The government, already embroiled in a year-long war against northern forces, dismissed the creation of the alliance as a stunt and accused some members of past ethnic violence. The alliance was announced by faction leaders in Washington despite calls from African and Western leaders for a national ceasefire, as federal troops battle the northern-based Tigray People"s Liberation Front (TPLF) and its allies. With the rebels threatening to move on the capital Addis Ababa, the Ethiopian army on Friday called on former personnel to rejoin the military to fight them, state media said. The U.N. Security Council on Friday called for an end to the fighting in Ethiopia and for talks on a lasting ceasefire as the 15-member body expressed deep concern in a rare statement about the expansion and intensification of military clashes. read more The council also "called for refraining from inflammatory hate speech and incitement to violence and divisiveness." The United States advised its citizens to leave Ethiopia as soon as possible. "The security environment in Ethiopia is very fluid," the U.S. Embassy said in a statement. The war, which has killed thousands of people and forced more than two million from their homes, has intensified in recent weeks. Announcing the formation of the United Front of Ethiopian Federalist and Confederalist Forces at an event in Washington, the alliance said it was setting up a command to coordinate military and political efforts. "The next step will be to organise ourselves and totally dismantle the existing government, either by force or by negotiation ... then insert a transitional government," said Mahamud Ugas Muhumed, of the Somali State Resistance, one of nine member groups, all of whom have armed units. The pact expands an existing agreement between the TPLF and the Oromo Liberation Army (OLA), organisers said. "We"re trying to bring an end to this terrible situation in Ethiopia, which is created single-handedly by the Abiy government," said Berhane Gebrekristos, a TPLF leader and former Ethiopian ambassador to the United States. "Time is running out for him." In a rejoinder, the government said it had a responsibility to secure the country, and urged its international partners to stand with Ethiopia"s democracy. "There is no equivalence between a democratically elected government and a group of terrorists and non-state actors that continue to cause violence and destruction," its communication service said in a statement. Abiy"s party won a landslide victory in June. Attorney General Gedion Temothewos called the alliance "a publicity stunt" and said some of the groups had a track record of "ethnic cleansing". He referred to only one of the groups, the OLA, accusing them of trying to commit "pogroms" in the western part of the Oromiya region. The OLA was not immediately reachable for comment on that. "STOP THE WAR" The conflict started in November 2020 when forces loyal to the TPLF, including some soldiers, seized military bases in Tigray. In response, Abiy sent more troops to the northern region. The TPLF had dominated national politics for nearly three decades but lost influence when Abiy took office in 2018. The TPLF accused him of centralising power at the expense of regional states. Abiy denies this. The TPLF and the OLA told Reuters they were now in the town of Kemise in Amhara state, 325 km (200 miles) from the capital. The TPLF had said on Tuesday its forces were also closing in on the town of Mille, which would enable them to cut off the highway linking neighbouring Djibouti to Addis Ababa. The government accuses the TPLF of exaggerating gains. On Friday, government spokesperson Legesse Tulu said fighting was still 80 km (50 miles) from Mille. He also said there was fighting at least 100 km (60 miles) north of Shewa Robit, a town in the Amhara region that is on the A2 highway, which links the capital to Ethiopia"s north. That would put fighting about 57 km (36 miles) south of Kombulcha, one of two towns the TPLF said it captured last weekend. The government said on Friday that a TPLF commander, Colonel Guesh Gebrehiwot, was captured on Thursday during fighting near Dessie in Amhara. The TPLF was unreachable for comment on that. It was not possible to independently confirm claims made by either side as communications in the area remained down. At a market on Addis Ababa"s outskirts, traders went about their business as usual but fewer shoppers were coming. Vegetable seller Abdisa Wili, 32, said prices were rising. "Both sides should stop the war, no one will profit from war except death and economic downfall," he said. "They should solve the problem through discussion." State-affiliated Fana TV reported that thousands of people took to the streets on Friday for pro-government rallies in at least seven towns and cities in Oromiya region, which surrounds Addis Ababa. Abiy is part Oromo and support from Ethiopia"s largest ethnic group helped propel him to power but he lost some backing when security forces detained thousands of Oromos read more Amnesty International said there has been an alarming rise in social media posts advocating violence. Twitter said it had removed an unspecified number of pro-government accounts for violating policies against deceptive content aimed at misleading or disrupting other users. There was no immediate comment on that from authorities in Addis Ababa.