Bulgarian citizen Kiril Elevterov and a UK citizen who were kidnapped in Nigeria on July 9 have been released.

The two were kidnapped in Delta state, a region rich in petrol, Bulgarian Foreign Ministry said.

Elevterov and the UK citizen were working for Nigeria's Manipolu oil company. Armed men in speedboats attacked a barge belonging to the company and kidnapped the workers. The incident occurred a day after three other foreigners were abducted from the area.

The workers were employed by the UK EXPROGROUP oil company in southern Nigeria.

Elevterov is expected to arrive in Bulgaria on August 9, the ministry said.

The release of the hostages happened thanks to the effort of Bulgarian and UK embassy representatives in Nigeria, the UK oil company and Nigerian authorities.

No information has been provided yet if ransom had been paid for their release.