ADDIS ABABA/NAIROBI, Oct 31 (Reuters) - Two different groups fighting Ethiopia"s central government said they had seized control of towns on Sunday as the prime minister appealed for citizens to take up arms. The spreading conflict threatens to further destabilise Africa"s second most populous nation, once considered a stable Western ally in a volatile region. Prime Minister Abiy Ahmed urged citizens to join the fight against the Tigray People"s Liberation Front (TPLF), the party in control of the rebellious northern region of Tigray, after Tigrayan forces said they took another town on a highway linking the capital of the landlocked nation to the port of Djibouti. "Our people should march...with any weapon and resources they have to defend, repulse and bury the terrorist TPLF," Abiy said in a Facebook post on Sunday night. CLAIMS OF GAINS TPLF spokesperson Getachew Reda said Tigrayan forces have seized the town of Kombolcha and its airport in the Amhara region. He spoke to Reuters by phone from an unknown location. On Sunday night, insurgents from Oromiya, Ethiopia"s most populous region, said they had also seized the town of Kemise, 53 km (33 miles) south of Kombolcha on the same highway to the capital Addis Ababa. Odaa Tarbii, a spokesperson for the Oromo Liberation Army (OLA), said the group had taken Kemise, 325 km (200 miles) from Addis Ababa, and were engaging government forces. The OLA is an outlawed splinter group of the Oromo Liberation Front, a formerly banned opposition group that returned from exile after Abiy took office in 2018. The Oromo are Ethiopia"s largest ethnic group; many of their political leaders have been imprisoned under Abiy"s government. In August the OLA and the TPLF announced a military alliance, heaping pressure on the central government. Central government spokesperson Legesse Tulu, Ethiopian military spokesperson Col. Getnet Adane and Amhara regional spokesperson Gizachew Muluneh did not immediately respond requests for comment on the TPLF and the OLA"s claims. Reuters could not independently verify Getachew"s claim as phone lines in Kombolcha appeared to be down on Sunday. Reuters could not reach anyone in Kemise. On Sunday, the Amhara regional government said in a statement "all government institutions must suspend their regular activities and should direct their budget and all their resources to the survival campaign....officials on every level should mobilise and lead...to the front." They announced a curfew of 8 p.m. and urged citizens to provide private vehicles to support the campaign. YEAR-LONG WAR War broke nearly a year ago between federal troops and the TPLF, which dominated Ethiopian politics for nearly three decades before Prime Minister Abiy Ahmed was appointed in 2018. The conflict has killed thousands of civilians and forced more than two million people to flee their homes. Tigrayan forces were initially beaten back, but recaptured most of Tigray in July. They then pushed into the neighbouring Amhara and Afar regions, displacing hundreds of thousands more civilians. Regional forces from Amhara have fought alongside the military in Tigray. The two regions of Amhara and Tigray have a long-running boundary dispute over farmland in Western Tigray, currently under the control of the Amhara administration. In mid-October, the Tigrayan forces said the military had mounted an offensive to push them out of Amhara. The military has accused the Tigrayan forces of starting the recent round of fighting. Tigrayan forces have said they will keep fighting until Amhara forces leave the heavily fortified area of Western Tigray, and until the government permits the free movement of aid into the rest of Tigray. The United Nations has previously accused the government of a de facto blockade of Tigray, where the U.N. says around 400,000 people are living in famine conditions. The government denies blocking aid.