Ethiopia has accused Egypt and neighbouring Eritrea of supporting outlawed rebels and stoking an unprecedented wave of protests that has led the government to declare a six-month state of emergency.
There is "ample evidence" that Egypt provided training and financing to the Oromo Liberation Front, a group labelled a terrorist organisation by Ethiopia, communication minister and government spokesperson Getachew Reda told journalists on Monday.
"We know for a fact that the terrorist group OLF is receiving all kinds of support from Egypt," he added.
"Its leaders used to be in Asmara (Eritrea) now they are in Cairo."
He said "elements in the Egyptian political establishment" were fomenting rebellion, seeking to promote "historical rights" over access to the River Nile.
Ethiopia is building a hydropower dam on the Nile close to its source in the Ethiopian highlands, raising fears in Egypt, which depends on controlling the flow of the Nile's waters for its survival.
Last week Ethiopia's foreign ministry summoned Egypt's ambassador to discuss "the current situation", according to Ethiopian state media.
Egypt, however, denied last week providing any support for the Ethiopian rebels.
"What we have is anti-Ethiopian elements using the protesters to attack whatever achievements Ethiopia has made in the last 15 or 20 years," said Reda.
"This has been done at the behest of historical enemies of the country," he said, accusing Eritrea of "infiltrating terrorists" into the country.
Eritrea and Ethiopia fought a two-year border war between 1998 and 2000 which left 80,000 dead, and tensions between the neighbours flared again earlier this year.
Ethiopia's government is facing the biggest challenge of its 25 years in power from protesters who have turned their anger against foreign-owned companies, torching several farms and factories in the past week.
Rights organisations have already criticised authorities for a harsh security crackdown on nearly a year of protests that has killed hundreds.
|We know for a fact that the terrorist group OLF is receiving all kinds of support from Egypt
- Getachew Reda
Earlier this month, more than 50 people were killed in a stampede after security forces opened fire on anti-government protesters during a religious festival in Bishoftu, southeast of the capital.
The incident sparked more violence in Oromia, where hundreds of local and foreign businesses have been attacked over suspected government ties and more people have been killed, according to both the government and opposition.
The government has said the state of emergency may include a curfew in some locations, arrests and search-and-seizures without a court order, restrictions on the right to assembly and a ban on some communications.
"Declaring a state of emergency at this time in Ethiopia is aimed at legitimising the killings that we have seen in the Oromia region recently," Mulatu Gemechu of the opposition Oromo Federalist Congress party told The Associated Press.
"It won't solve the public's problems and will only worsen it. What people are looking for is a radical change. The people now want the setting up of a transitional or caretaker government."
The protests, which first began in November 2015, threaten Ethiopia's reputation as an oasis of political stability whose double-digit growth has lured investors in recent years.