Prime Minister Abiy Ahmed unleashed a military campaign in the country's northern region on November 4 with the declared aim of unseating its ruling party, the Tigray People's Liberation Front (TPLF), which he accuses of defying his government and seeking to destabilise it.

Army chief Berhanu Jula told a press conference that Tedros, who served as health minister under TPLF leader Meles Zenawi, was "a part of that team", referring to the party.

"He has worked in neighbouring countries to condemn the war. He has worked for them to get weapons," said Berhanu, without offering evidence to support the claims.

He added that Tedros had "left no stone unturned" to help the TPLF.

In a separate press conference, Redwan Hussein, spokesman for a crisis committee handling the conflict, admitted "the government is not happy" with Tedros.

"The government is aware that he has been hustling and bustling, calling leaders and... institutions and asking them to... compel the government to sit and negotiate," he said.

"The government actually expects him to reach out and ask... as to how he might be of use or help to the government."

Tedros has yet to respond to the accusations.

The 55-year-old was appointed as the first African head of the WHO in 2017 and has become a household name as he grapples with the Covid-19 pandemic. He has been ranked as one of Time magazine's most influential people.

Abiy's government insists its target is the "reactionary and rogue" members of the TPLF and not average civilians in Tigray.

But observers have voiced concern about Tigrayans losing their jobs or being arrested for their ethnicity.

- 'Closing in on Mekele' -

The TPLF led the overthrow of Mengistu Hailemariam, head of Ethiopia's military Derg regime, in 1991 and dominated politics for three decades until the arrival of Abiy who was appointed in 2018.

The party has complained about being sidelined under Abiy, and scapegoated for the country's woes. The bitter feud with the central government this year led the TPLF to hold their own elections in defiance of a postponement due to the pandemic.

On November 4, Abiy said the TPLF had attacked two federal military camps in the region, crossing a "red line".

His controversial campaign has seen warplanes bombing Tigray and heavy fighting, while Amnesty International has documented a gruesome massacre.

A communications blackout in Tigray has made claims difficult to verify, but the overall toll is believed to be in the hundreds.

Abiy this week insisted the military operation was in its final phase.

Redwan said that "our defence forces are moving forward and closing in on Mekele," the regional capital.

He added that the northern town of Shire, where heavy fighting has been reported in recent days, was already in government hands.

A senior Tigrayan official, Wondimu Asamnew, said that Tigrayan forces "have adopted a defensive posture on all fronts".

A statement from Tigray president Debretsion Gebremichael on Thursday said the army had "called upon assistance from an outside force, with drones starting to be used in the battle."

Meanwhile the UN says a "full-scale humanitarian crisis" is unfolding, with 36,000 people having streamed into neighbouring Sudan, according to that country's refugee commission.

Redwan said that the government was planning to "convince and bring back our compatriots from Sudan and preparations are underway here."

He said the government had also sent "fact-finding missions" to determine the best way to get food and medical items to Tigray.

- 'Alienating Tigrayans' -

Since the start of fighting, hundreds of people have been arrested for allegedly conspiring with the TPLF, while 34 businesses had their bank accounts suspended for alleged links to the TPLF.

The federal police late Wednesday announced arrest warrants for 76 army officers, some retired, accused of conspiring with the TPLF and "committing treason".

The government has also said it has "credible and specific evidence" of TPLF operatives working for local and international organisations.

"We continue to receive credible reports of job suspensions of Tigrayan residents elsewhere in the country as fighting escalates in Tigray," Laetitia Bader of Human Rights Watch told AFP last week.

"Given the incredibly tense and volatile context in the country, Ethiopian authorities should push back against language and measures that fuel intolerance and risk alienating Tigrayans from all walks of life."