Ethiopia and Eritrea had been at war for 20 years over the location of boundaries between the two countries.
Celebrating their dramatic diplomatic thaw, the leaders of Ethiopia and Eritrea on Tuesday officially opened the border where a bloody war and ensuing tensions had divided them for decades.
Ethiopia's reformist new Prime Minister Abiy Ahmed and longtime Eritrean President Isaias Afwerki visited the Bure Front along with members of their militaries to mark the Ethiopian new year, Abiy's chief of staff Fitsum Arega said in a Twitter post.
The two then opened the border post "for road transport connectivity" and would shortly do the same at the Serha-Zalambesa crossing, Eritrean Information Minister Yemane Meskel said on Twitter.
Photos posted by both officials showed Abiy in camouflage and sunglasses walking alongside Isaias in olive drab, while civilians lined a road with the countries' flags in hand.
The former bitter rivals have made a stunning reconciliation since Abiy weeks after taking office in April announced that Ethiopia would fully embrace a peace deal that ended a 1998-2000 border war that killed tens of thousands.
At the time, he announced that the countries would celebrate the Ethiopian new year together, "We want our brothers and sisters to come here and visit us as soon as possible."
Since signing an agreement in Asmara on July 9 to restore ties, the Eritrean and Ethiopian leaders have moved swiftly to end two decades of hostility.
Eritrea reopened its embassy in Ethiopia in July, and Ethiopia reciprocated last week.
Embassies have reopened, telephone lines have been restored and commercial flights between the capitals have resumed as some long-separated families have held tearful reunions.
TRT World talks to journalist Coletta Wanjohi who explains the significance of this reconciliation.
Landlocked Ethiopia, one of Africa's fastest-growing economies, and Eritrea, one of the world's most closed-off nations, also plan development co-operation around Eritrea's Red Sea ports in particular.
Reports on social media on Monday indicated that mine-clearing activities were underway in one border area, signaling that an opening was planned.
Abiy on Monday told a new year's eve concert crowd of thousands in Ethiopia's capital, Addis Ababa, that "as of today, Ethiopian and Eritrean people will prosper together and march in unison. ... The last five months have brought hope and reconciliation."
The reconciliation between Ethiopia and Eritrea has been warmly welcomed by the international community and has led to a series of further thaws in the fragile Horn of Africa region, with Eritrea resuming diplomatic ties with both turbulent Somalia and the small but strategic port and military nation of Djibouti.