Dozens of passengers on a bus in Ethiopia have been abducted by armed men in the country's largest region, Oromia, as they were travelling from the capital, Addis Ababa.

Details are only just emerging of the kidnappings, which took place earlier this week.

The incident happened in Ali Doro, which is near an area where around 100 university students were similarly abducted as they were heading home from their campus last July.

Survivors and local authorities blamed those abductions on the Oromo Liberation Army (OLA), a rebel group that operates in the area. The group denied involvement at the time.

Referring to this week's incident, the OLA has said it had received reports of the abductions and that it was "conducting an investigation".

According to one report by a local media organisation, the passengers were heading to Debre Markos, a town in the country's Amhara region, when they were attacked by the armed men, who exchanged fire with local security forces.

Another report said several buses were attacked, during which at least one person died. The number of abductees could be as high as 50, according to this report.

The government has not yet said anything about the kidnappings, and the BBC's attempts to get an official response have been unsuccessful.

Abductions of civilians - including passengers - have become increasingly common in the area. Armed groups here have in the past demanded ransoms for the release of the people they hold.

The OLA says it is fighting for the self-determination of Ethiopia's largest ethnic group, the Oromo.

It has been classified as a terrorist organisation by the federal parliament and operates in various areas in Oromia, including the district where Ali Doro is located.