ADDIS ABABA, July 1 (Reuters) - Ethiopia"s government urged Tigrayan rebels to join a unilateral ceasefire in their conflict on Thursday as aid agencies struggled to reach hundreds of thousands of people facing famine. The Tigray People"s Liberation Front (TPLF), the former rulers of Ethiopia"s Tigray region, said on Monday it was back in control of the regional capital Mekelle after nearly eight months of fighting. The government declared a unilateral ceasefire but the TPLF dismissed it as a joke. Hostilities persisted on Thursday and pressure built internationally for all sides to pull back. "Operations are under way ... and the number of prisoners of war is increasing by the minute,” TPLF spokesman Getachew Reda told Reuters by satellite phone, with light artillery fire crackling in the background. "We are closing in on both the western and southern parts of our territory and will be measuring our steps so we can fully liberate every square inch of Tigray." A bridge over the Tekeze River near the northern town of Shire has been destroyed, so getting aid to the region will be "even more severely hampered" than before, the International Rescue Committee said. "We are deeply concerned regarding the implications this will have for humanitarian access to areas facing dire and life-threatening needs," said Gemma Connell, head of the U.N. Office for the Coordination of Humanitarian Affairs for Southern and Eastern Africa. Shire and several other towns in Tigray are now controlled by the Tigrayan forces. Government-allied forces from the neighbouring region of Amhara control territory on the other side of the Tekeze River. "For this (ceasefire)to be fully implemented, as they say, it needs two to tango, so the other side needs to react," Ethiopian foreign ministry spokesman Dina Mufti said. Mufti said it was not yet clear "how and which way is aid going to enter and what is going to happen with flights." With electricity and phone and internet lines cut to the region, aid agencies are limited in their ability to reach people in need of food and other services. Hospitals in Mekelle are running on generators, said Alyona Synenko, a spokesperson for the International Committee of the Red Cross. The United Nations said in early June at least 350,000 people in Tigray faced famine. The U.S. Agency for International Development last week estimated the number at 900,000. "It is urgent to get additional staff and supplies into Tigray, restore electricity and telecoms, and ensure that cash and fuel are available throughout the region for the continuity of humanitarian operations," an OCHA spokesperson, Hayat Abu Salah, said. SATELLITE EQUIPMENT DESTROYED In Mekelle, the streets were calm on Thursday morning and markets were open for business, Abu Salah said. Electricity and telecommunications remained down and U.N. offices were relying on limited remaining satellites after Ethiopian soldiers destroyed equipment at the UNICEF office in the city, she said. On Wednesday, the United Nations was able to conduct assessment missions to several towns now back under TPLF control, she said. "We are preparing for resumption of aid," Abu Salah said, adding that 5.2 million people were in need of assistance in Tigray. Prime Minister Abiy Ahmed acknowledged government troops had left Mekelle after months of fighting, saying it was because the city was no longer the "centre of gravity for conflicts". read more He said Ethiopian forces had left Mekelle to focus on more important security threats. A TPLF spokesman said government troops were forced out. Abiy has faced mounting international pressure to bring an end to the conflict, which has been punctuated by reports of gang-rapes and mass killings of civilians. At least 12 aid workers have been killed. Abiy has acknowledged atrocities have occurred. His government has been battling the TPLF since late last year, when it accused the then-governing party of Tigray of attacking military bases across the region. Thousands have been killed. Abiy said on Tuesday his government had spent more than 100 billion birr ($2.3 billion) on rehabilitation and food aid for the region, equivalent to 20% of this year"s national budget. Abiy said some of the aid was falling into the hands of the “junta”, a reference to the TPLF, and reaching combatants rather than civilians. U.N. Secretary General Antonio Guterres said on Monday he hoped a political solution would be possible. The United States and Britain said atrocities should end immediately. "The violence must now stop and unfettered humanitarian access granted," a spokesman for Britain"s Foreign Office said on Thursday. "Eritrean forces should also leave Tigray."