The British foreign office said that a number of British nationals connected to government agencies were missing in Ethiopia.
"We can confirm that a group of Western tourists is missing in eastern Ethiopia including a number of British nationals with connections to the British Council, the Foreign Office and the Department for International Development," the ministry said.
Margaret Beckett, Britain's foreign minister, later said that some of the British contingent were from the British embassy in Ethiopia.
"Unfortunately I can confirm that five of those [missing] are members of staff, or relatives of members of staff, at our embassy in Addis Ababa," Beckett said in a statement.
An official from the Origins Ethiopia tour group earlier told AFP news: "In the first convoy, there were 11 French, my guide, three drivers, a cook, two policemen.
"The other group had three British residents in Ethiopia, a cook, a guide, and two policemen."
He said he had lost contact with the guide accompanying the tourists on Tuesday night.
"A driver of one of my colleagues called me yesterday to inform me that one or two of my groups have been kidnapped," he said.
Ethiopia's government said it was aware of this week's incident, but could not confirm if it was a kidnapping.
"The government is monitoring the situation," an information ministry spokesman said.
The government requires all convoys visiting the area to have a minimum of two cars and travel with armed guards because of the threat of bandits.
In 1995, nine Italian tourists were captured by Afar tribesmen, then released two weeks later.
Afar separatists began a low-level rebellion against the Addis Ababa government in the 1990s, calling for the creation of a separate Afar state on territory which straddles Ethiopia, Eritrea and Djibouti.