Given deep antipathy between the Tigrayans and Abiy, who comes from the largest Oromo ethnic group, there are fears of civil war and knock-ons around the Horn of Africa region
* Thousands flee week-long fighting in Tigray state
* Hundreds reported killed in PM Abiy's offensive
* Conflict could destabilise Ethiopia and wider region
NAIROBI, Nov 11 (Reuters) - Thousands of Ethiopian refugees were fleeing into neighbouring Sudan on Wednesday as federal troops continued 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 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 5 million people, where federal warplanes 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 Abiy won the 2019 Nobel Peace Prize, but both governments have long-held grudges against the TPLF.
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 6,000-7,000 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.
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 Abiy is intent on crushing the Tigrayan leaders and not ready to mediate.
"We won't rest till this junta is brought to justice," he tweeted late on Tuesday.
A former soldier who once fought alongside Tigrayans against Eritrea, 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.
In Ethiopia's capital Addis Ababa, an explosion under a bridge blew off a man's leg, but there was no indication it was related to the Tigray fighting.
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.
Spokesmen for the federal police and Attorney General's office, where the prime minister's spokeswoman referred Reuters for comments, did not respond to calls and messages.
Quelling Tigray may be tough for 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.
Though there was little detail from the ground, the fighting will be worsening the humanitarian situation in Tigray, where there were already 100,000 internally displaced people and 600,000 dependent on food aid.
(Reporting by Nairobi Newsroom; Writing by Maggie Fick, Duncan Miriri and Andrew Cawthorne; Editing by Nick Tattersall)
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