Signs of change. BBC Foreign Affairs correspondent James Robbins reports.

Hilary Andersson: "his release is only a matter of time"

He was speaking at a news conference in the capital, Abuja, at the end of a visit aimed at securing the release of the country's top political prisoner, Moshood Abiola.

Mr Annan said the the government would make the announcement at "the appropriate time."

"Abiola said he would want to be released to get on with his life. He told me 'I am not naive enough to think I can come out and be president,'" the UN Secretary-General said.

Annan meets new Nigerian leader General Abubakar (UN Photo)

This appears to settle what had been the major issue holding up his release - some of Chief Abiola's supporters had been calling for him to take up the post which observers believe he won in the 1993 presidential elections annulled by the military government.

Mr Annan and the Commonwealth Secretary General, Emeka Anyaoku were allowed to visit him in a safe house in Abuja on Wednesday - the first independent international figures to see Chief Abiola in two years.

In good health

Mr Anyaoku said Chief Abiola's political standpoint had changed little in the last few years and that he appeared well, despite four years in solitary confinement.

Pictures released of the opposition leader meeting the UN Secretary-General show him in apparent good health, though he has lost weight.

Both Mr Annan and the Commonweath Secretary-General have held talks with Nigeria's new military ruler Abdulsalam Abubakar this week as part of the international effort to restore democracy in the country.

On Wednesday the Nigerian Foreign Minister, Chief Tom Ikimi, gave the strongest indication yet that Chief Abiola would be released soon.

Political role possible

Speaking in a BBC interview, the foreign minister said he saw the possibility of a future political role for Chief Abiola, who is widely believed to have won the presidential elections annulled by the military in 1993.

But Chief Ikimi repeated hints that the government wants him to renounce his claim to a presidential mandate before being freed.

John Oyegun, spokesman for the opposition umbrella group NADECO, told the BBC he hoped that Chief Abiola would play a significant role in future politics.

"There is no room anymore for the military in Nigerian politics," he said, reacting to the UN Secretary-General's statement. "Chief Abiola must be a part of the reconciliation and the reconstruction that we envisage for Nigeria."

The high-level visits are being seen as the biggest sign yet of foreign confidence in General Abubakar, who took over earlier this month after the sudden death of Sani Abacha.