NAIROBI, Kenya (AP) — Ethiopian military airstrikes on Friday forced a United Nations humanitarian flight to abandon its landing in the capital of the country’s Tigray region, and a government spokesman said authorities were aware of the inbound flight. It appeared to be a sharp escalation in intimidation tactics authorities have used against aid workers amid the intensifying, year-long Tigray war.

Further U.N. flights have been suspended to Mekele, the base of humanitarian operations in Tigray, the World Food Program told The Associated Press. It said the flight with 11 passengers had been cleared by federal authorities but “received instructions to abort landing by the Mekele airport control tower.” It safely returned to Addis Ababa.

U.N. humanitarian chief Martin Griffiths said: “The U.N. had not received any prior warning of the attacks on Mekelle and had received the necessary clearances for the flight.”

He expressed “grave concern” for civilians facing airstrikes in Mekele and insufficient humanitarian assistance into Tigray, and alarm at the worsening toll of fighting on civilians in the neighboring Amhara and Afar regions.

“We’ve had flights turned around because of weather," Gemma Connell, head of the U.N.’s regional humanitarian office for southern and eastern Africa, told reporters. “But this is the first time we’ve had a flight turn around, at least to my knowledge, in Ethiopia because of airstrikes on the ground.”

The friction between the government and humanitarian groups is occurring amid the world's worst hunger crisis in a decade, with close to a half-million people in Tigray said to be facing famine-like conditions. The government since June has imposed what the U.N. calls a “de facto humanitarian blockade” on the region of some 6 million people, and the AP has reported that people have begun to starve to death.

Ethiopian government spokesman Legesse Tulu told the AP authorities were aware the U.N. flight was in the area but said the U.N. and military flights had a “different time and direction.” It wasn’t immediately clear how close the planes came to each other.

Tigray forces spokesman Getachew Reda in a tweet said “our air defense units knew the U.N. plane was scheduled to land and it was due in large measure to their restraint it was not caught in a crossfire.” He suggested that Ethiopian authorities were “setting up the U.N. plane to be hit by our guns.”

A military spokesman didn’t respond to questions.

Legesse said Friday’s airstrikes in Mekele targeted a former military training center being used as a “battle network hub” by rival Tigray forces. Residents said they hit a field near Mekele University. Tigray spokesman Kindeya Gebrehiwot told the AP about a dozen people were wounded.

Ethiopia’s government in recent months has accused some humanitarian groups of supporting the Tigray forces, and last month it took the extraordinary step of expelling seven U.N. officials while accusing them without evidence of falsely inflating the scale of the Tigray crisis. Authorities have subjected aid workers on U.N. flights to intrusive searches and removed medical cargo.

Meanwhile, the U.N. says just 1% of the targeted 5.2 million people in urgent need received food aid between Oct. 7 and 13. Now the airstrikes that began this week in Mekele have halted aid deliveries, the U.,N.'s Connell said, adding that “not a single truck” has entered Tigray since Monday.

Thousands of people have been killed since November, when a political falling-out between the Tigray forces who long dominated the national government and the current administration of Prime Minister Abiy Ahmed erupted in fighting.

Tigray forces in recent months have retaken the Tigray region and brought the fighting into the neighboring Amhara and Afar regions. The U.N. says more than 2 million people are now displaced overall.

And yet “our operations will come to a grinding halt in the not so distant future” in Tigray if current conditions continue, Connell said.

The airstrikes in Mekele were the first in several months, killing three children and injuring more than a dozen people, despite repeated international calls for a cease-fire and the threat of further sanctions.

On Thursday, the government claimed a successful strike against another military base used by the Tigray forces near Mekele, but the Tigray forces spokesman asserted that air defenses prevented the plane from hitting targets.

An airstrike on Wednesday hit an industrial compound the government said was used by the Tigray forces to repair weapons. A Tigray spokesman denied that and said it was used to produce cars and tractors. Two other airstrikes hit the city on Monday.

Tigray remains under a communications blackout, making it difficult to verify claims, while areas of fighting in Amhara are largely unreachable as well.

The airstrikes come amid reports of renewed heavy fighting in Amhara. On Wednesday, the Tigray forces spokesman claimed advances had put the government-held towns of Dessie and Kombolcha “within artillery range,” prompting alarm.

Dessie hosts a large number of displaced people who have fled fighting further north. One resident told the AP he has seen many cars leaving the town with mattresses, cooking equipment and other household items strapped to their roofs in the last few days, but many displaced people are stuck because they can’t afford to leave.

He also reported plenty of vehicles carrying troops north to the front and the constant sound of shelling. He spoke on condition of anonymity for fear of retribution.

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