Within a month in 1998, Nigeria lost both its military ruler Sani Abacha and its main opposition figure, Chief Moshood Abiola.

Nigeria's recent political history was shaped by the dominating personalities of these two men. With their deaths, the political landscape has been transformed.

World leaders called on the government of General Abdusalam Abubakar to continue with the transition to civilian rule, which was due to take place by October 1.

The United Nations Secretary General Kofi Annan said: "I hope the government of Nigeria will make good on its pledge to release all remaining political prisoners unconditionally and to define a credible process for the democratic transition to civilian rule within a reasonable period," he said.

Nigeria's long-serving ambassador to the UN, Ibrahim Gambari, said he believed that Nigeria would indeed go ahead with the planned transition process. But new plans have yet to be unveiled by military leader General Abubakar.

No obvious opposition successor

Chief Abiola's death left the Nigerian opposition movement divided and without an obvious successor. Among those leaders critical of the military government are:

• General Olusegun Obasanjo - a former head of state, recently released from prison, he had been vocal in calling for the early release of Abiola.

• The Group of 34 - a collection of politicians who opposed General Abacha's transition programme, representing a spectrum of opinion. Prominent among them are Dr Alex Ekwueme and Chief Solomon Lar.

• Chief Gani Fawehinmi - a prominent lawyer who has defended many political dissidents. He has been imprisoned himself more than any other opposition leader.

• Senator Abraham Adesanya - a pro-democracy leader and head of the country's main umbrella opposition group NADECO

• Olisa Agbakova- a leader of United Action for Democracy and a prominent human rights lawyer.

Mixed feelings over Abiola

Abiola - not considered fit to rule by all

Part of the problem for the opposition is that many had severe doubts about Chief Abiola's ability to lead Nigeria. It was pointed out that he had made his fortune partly by doing business deals with the military.

Others were angered by reports that he was about to renounce his presidential mandate in exchange for his freedom.

Chief Abiola also alienated support among Muslims in the North, who had previously backed him, but were subsequently accused of conspiring with the military to keep him out of power.

Need for military to restore credibility

What to do about Chief Abiola was the most delicate issue faced by the new and potentially more flexible military leadership. His detention was one of the main reasons for continued international santions, but as long as he called himself the rightful elected leader of Nigeria, his freedom could destabilise the new political process about to be announced.

Now he has gone from the scene and many see this as altogether too convenient.

Speculation that Chief Abiola's death was not an accident has fuelled the wave of rioting and protests in southern Nigeria, the political stronghold of the opposition leader.

"I think the first thing the government has to deal with is to appease his supporters and to deal with the immediate political aftermath of his death," said the BBC Nigeria correspondent Hilary Andersson.

How the military responds to a political backlash which has abruptly ended their political honeymoon will reveal much about their long term intentions on human rights and democracy.

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