Hundreds of Ethiopians gathered Thursday to donate blood for troops fighting in the northern Tigray region, as officials tried to rally support for a week-old conflict Prime Minister Abiy Ahmed said was going his way.

The government also announced that police had arrested 150 people in the capital suspected of trying to carry out "terror attacks" on the orders of Tigray's ruling party.

Prime Minister Abiy blames the Tigray ruling party for a conflict that analysts fear could spiral into a protracted civil war.

Hundreds have died and thousands have fled the country since Abiy, last year's Nobel Peace Prize winner, sent troops and warplanes into Tigray last week after a months-long feud with the Tigray People's Liberation Front (TPLF).

Abiy said the TPLF -- which dominated Ethiopian politics for nearly three decades before he took office in 2018 -- had crossed a "red line" and attacked two federal military bases, which the party denies.

Thursday's blood drive was organised by the office of Addis Ababa Mayor Adanech Abebe, who claimed the population was unified against the TPLF while donating blood herself.

"The aim of this blood donation is to express our respect for our army," she told journalists as a nurse drew blood from her left arm.

"The attack done by TPLF to our army is shameful for Ethiopia. Never happened in our history. We want to condemn this."

Tigray has been under a communications blackout since the military operation was launched on November 4, making it difficult to verify the situation on the ground as both sides make conflicting claims.

In a Facebook post Thursday, Abiy said government forces had "liberated" the western zone of Tigray -- made up of six zones, plus the capital and surrounds.

Abiy also accused TPLF-aligned fighters of "cruelty", saying that when the army took control of the town of Sheraro they "found bodies of executed defence force personnel whose hands and feet were tied". There was no immediate reaction from the TPLF.

Under Abiy, Tigray's leaders have complained of being unfairly targeted in corruption prosecutions and removed from top positions.

Tensions soared as Tigray defiantly held its own elections in September, insisting Abiy was an illegitimate leader after national polls were postponed due to the coronavirus.

-'Rule of law'-

The conflict has seen multiple rounds of airstrikes targeting arms and fuel depots along with heavy fighting in western Tigray.

The UN said Wednesday some 11,000 Ethiopians had sought refuge in neighbouring Sudan, and Ethiopia has acknowledged some of its troops at one point retreated into neighbouring Eritrea, highlighting the conflict's potential to draw in the wider Horn of Africa region.

Sudanese Prime Minister Abdalla Hamdok, quoted by state news agency SUNA as he hosted Eritrean Foreign Minister Osman Saleh, on Wednesday called for a "stop to the fighting as soon as possible" and a return to the negotiating table.

The African Union has also called for an immediate stop to fighting and for dialogue, as internationa