Madrid, Apr 22 (IANS/EFE): Spanish physician Jose Manuel Machimbarrena, kidnapped in Nigeria April 4, has been freed and is in good health though "pretty tired", officials at Spain's foreign ministry said Saturday.

The 58-year-old doctor was set free Friday by his captors at an unidentified location, and is now back in the southern Nigerian city of Enugu where he has lived for many years.

The circumstances under which he was released and whether any ransom was paid have not yet been made clear.

In recent years, Enugu has suffered a growing number of abductions, mostly carried out to demand ransom money.

The problem became so serious in 2009 that the federal government enacted a law making kidnapping at gunpoint a crime punishable by death.

In a communique to the media Saturday, the Nigerian police said that Machimbarrena "looks well, healthy and happy", and is currently back with the "hospital community" in Enugu.

The note also said that Nigerian security forces have stepped up "the search for the outlaws" who kidnapped him and whose identity is unknown.

Dr. Machimbarrena, director of clinical services at the Niger Foundation Hospital, an Opus Dei project, has lived in Nigeria since 1978.