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• Coups no longer 'fashionable'
• Encouraging words from U.N. envoy
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ABUJA, Nigeria (CNN) -- As Nigeria prepares for a crucial first vote under military ruler Gen. Abdulsalami Abubakar's plan to restore civilian rule, Abubakar told the armed forces they must give up power forever next May.

The call came as a special U.N. envoy for Nigeria commented favorably on reforms in the country, saying there was a "noticeable change in the political atmosphere and in the attitude of the administration."

Abubakar -- who assumed power after the sudden death of dictator Gen. Sani Abacha in June -- has pledged to relinquish military rule and restore a civilian administration in May. Saturday's local government elections are seen as a crucial test of the country's path toward democracy.

"Coup-making has long ceased to be fashionable and anyone who may not have come to terms with that reality is only engaging in self-delusion," Abubakar told the military on Tuesday in a strongly worded message that was also addressed to the police.

Saturday's local elections mark the first step in returning civilian administration to the West African country, which has been ruled by the military for all but 10 years since independence from Britain in 1960.

"A major consequence of prolonged military rule has been the grave lessening of professionalism among officers and men to which all of you gathered here are living witness," said Abubakar, referring to the loss of military officers to political posts.

Abubakar on Tuesday passed four decrees giving legal backing to his plan of restoring civilian rule and guaranteeing the independence of the electoral commission, according to Nigerian national television.

U.N. envoy Soli Sorabjee spoke on Tuesday of a big improvement in human rights in Nigeria under Abubakar, but added that existing repressive decrees should be scrapped.

Sorabjee made his comments at the end of a 10-day visit to the West African country.

"The one impression which I definitely have is that there is a noticeable change in the political atmosphere and in the attitude of the administration," Sorabjee told a news conference in Lagos.

Oil-producing Nigeria, Africa's most populous nation with at least 108 million people, has rapidly won favor in the world since Abubakar freed most detainees and pledged to step down in May.

However, Sorabjee also said that the ruling generals should abolish controversial laws, such as those which allow for indefinite detention without trial.

Reuters contributed to this report.