Theresa May has said she was “deeply saddened” to learn 157 passengers and crew-members were killed when an Ethiopian Airlines flight crashed shortly after take-off.
Seven Britons and one Irish citizen were among the dead after the jet crashed on Sunday morning, as were doctors, aid workers and three members of a Slovakian MP's family.
The Foreign Office confirmed that at least seven Britons were on board flight ET302, which crashed at about 8.45am leaving no survivors. Ethiopian Airlines said an Irish citizen was also on board.
In a statement posted to Twitter, the Prime Minister said: "I was deeply saddened to hear of the devastating loss of life following the plane crash in Ethiopia.
"At this very difficult time my thoughts are with the families and friends of the British citizens on board and all those affected by this tragic incident."
The airline said it had contacted the families of all victims, who came from 35 nations.
The Prime Minister's comments come as details begin to emerge about the people who were on board the plane, which crashed near the town of Bishoftu.
Many of the passengers were from Kenya, but others were said to be from Italy, France, the US, Canada, Ethiopia, China, Egypt, Germany, Slovakia and India.
Anton Hrnko, an MP for the nationalist Slovak National Party, said he was "in deep grief" to announce that his wife Blanka, daughter Michala and son Martin were among the victims.
Hospitality company Tamarind Group announced "with immense shock and grief" that its chief executive Jonathan Seex was among the fatalities and Paolo Dieci, a founder of an aid group that works with Unicef in Africa, was also reported as among the dead.
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Other victims included three members of Italian humanitarian organisation Africa Tremila, with the mayor of Bergamo announcing the aid group's president Carlo Spini, his wife, and treasurer Matteo Ravasio were killed in the crash.
Sicilian regional culture ministry assessor Sebastiano Tusa was also reportedly on the plane.
Ethiopian Airlines plane crash
The African Diaspora Youth Forum in Europe said co-chairman Karim Saafi had been a passenger on the flight and had been due to represent them at a meeting with the African Union in Nairobi.
"Karim's smile, his charming and generous personality, eternal positivity, and his noble contribution to youth employment, diaspora engagement and Africa's socio-economic development will never be forgotten," a statement said.
Austrian media reported that three doctors who were aged between 30 and 40 and worked at hospitals in Linz had died.
While the cause is not yet known, the crash shared similarities with last year's Lion Air jet plunging into the Java sea, killing 189. That also involved a Boeing 737 Max 8 crashing minutes after takeoff.
On Sunday, visibility was clear but air traffic monitor Flightradar24 said "vertical speed was unstable after take off".
The pilot had sent out a distress call and was given the all clear to return, according to the airline's chief executive Tewolde Gebremariam.
Senior captain Yared Getachew had a "commendable performance" having completed more than 8,000 hours in the air, the airline said.
The plane had flown from Johannesburg to Addis earlier on Sunday morning, and had undergone "rigorous" testing on February 4, a statement continued.
Records show the plane was new and delivered to the airline as recently as November.
An eyewitness told the BBC there was an intense fire when the plane crashed.
"The blast and the fire were so strong that we couldn't get near it," he said. "Everything is burnt down. There are four helicopters at the scene now."
Mr Gebremariam was pictured leafing through what little was left of the wreckage as he visited the freshly ground earth under the blue sky of Ethiopia's capital.
Minister Therese Coffey said no officials from the Department for Environment, Food and Rural Affairs (Defra) were on board, though she suspected some of the passengers had been travelling to the UN Environment Assembly in Nairobi.
UK investigators from the Air Accidents Investigation Branch are likely to be communicating with their counterparts in Ethiopia to keep next-of-kin informed.
A statement from Boeing said the manufacturer was "deeply saddened" to learn of the disaster, adding that it was sending a technical team to the crash site
The last fatal Ethiopian Airlines passenger plane crash was in 2010 when all 90 on board were killed when the aircraft crashed minutes after take-off from Beirut.
A Foreign Office spokeswoman said: "Following the Ethiopian Airlines crash, we can confirm at least seven British nationals were on-board flight ET302.
"Our staff at the British Embassy in Addis Ababa are in touch with the relevant authorities in Ethiopia. We extend our deepest condolences to all those who have lost loved ones and those affected by this tragic event."
Ireland's Department of Foreign Affairs and Trade said it was "aware of the incident and providing consular assistance".