Thousands of Ethiopian refugees are fleeing into neighbouring Sudan as federal troops continue to battle local forces in the closed-off northern Tigray region.

With outsiders barred and communications down, the status of Prime Minister Abiy Ahmed’s week-long offensive against regional rulers of the Tigray People’s Liberation Front (TPLF) was unclear.

Half a dozen journalists have been arrested, according to the country’s human rights commission, raising fears of an erosion of recent democratic advances in Ethiopia.

Security sources and state media have spoken of hundreds of deaths in the mountainous state of more than five million people, where federal war planes have been bombing arms depots as soldiers fight on the ground.

Given deep antipathy between the Tigrayans and Abiy, who comes from the largest Oromo ethnic group, and ethnic frictions elsewhere around Ethiopia, there are fears of civil war and knock-ons around the Horn of Africa region.

Ethiopia reached a peace agreement with neighbouring Eritrea two years ago, for which Mr Abiy won the 2019 Nobel Peace Prize, but both governments have long-held grudges against the TPLF.

Mr Abiy’s government also has troops deployed in Somalia helping to combat an Islamist insurgency.

United Nations sources told Reuters the Tigray conflict had already sent 6000 to 7000 people fleeing across the border into Sudan, with Khartoum fearing that number could balloon.

“The number is increasing around the clock,” said Alsir Khaled, an official from the Sudanese refugee commission.

Mr Abiy, who at 44 is Africa’s youngest leader, launched operations in Tigray last week after accusing the local government there of attacking a military base.

The United Nations, African Union and others are calling for a ceasefire, but diplomats and security officials say Mr Abiy is intent on crushing the Tigrayan leaders and is not ready to mediate.

“We won’t rest till this junta is brought to justice,” he tweeted late on Tuesday.

Our law enforcement operations in Tigray are proceeding as planned: operations will cease as soon as the criminal junta is disarmed, legitimate administration in the region restored, and fugitives apprehended & brought to justice — all of them rapidly coming within reach.

— Abiy Ahmed Ali 🇪🇹 (@AbiyAhmedAli) November 10, 2020

A former soldier who once fought alongside Tigrayans against Eritrea, Mr Abiy took office in 2018 after a Tigrayan-led government had dominated politics since rebels from their region toppled Marxist military rule in 1991.

But his efforts to open up a repressive political climate also led to an explosion of ethnic problems, with hundreds killed and hundreds of thousands forced to flee their homes in clashes over the last two years.

The government of Oromiya, the largest of Ethiopia’s nine ethnic-based regions with around 35 million people, called for protests against the TPLF and against an armed group from Oromiya.

The state-appointed human rights commission said that six Ethiopian journalists had been arrested.

“We reiterate our call for the respect of due and fair process,” commission head Daniel Bekele tweeted.

The Committee to Protect Journalists, a global watchdog, warned of “a dangerous reversal” of the Abiy government’s past steps to improve press freedom.

Quelling Tigray may be tough for Mr Abiy, experts say.

The TPLF are a battle-hardened movement, having been at the forefront of the 1998-2000 war with Eritrea and the defeat of Mengistu Haile Mariam in 1991.

Their forces and militia are well armed and number up to 250,000 men.