Brigadier-General Fred Chijuka would not reveal the sentences and said it was up to the Provisional Ruling Council to confirm the judgment.
Local newspapers and human rights activists have said some officers, including Brig-Gen Lawan Gwadabe, once General Abacha's principal staff officer, have been given death sentences, while Mr Obasanjo received a 25-year jail term.
The announcement came after weeks of speculation about the case, especially against Mr Obasanjo, a former army genral. His conviction was expected to heighten international pressure on the Abacha government but do little to strengthen domestic opposition. Mr Obasanjo angered his traditional supporters among the Yorubas of southwestern Nigeria by failing to support Moshood Abiola, winner of the 1993 presidential elections annulled by the military.
The Abacha regime, which came to power in November 1993, has faced a wave of international criticism over its poor human rights record, particularly its detention of Mr Obasanjo and human rights activists, and its alleged suppression of a campaign by the Ogoni people to demand a greater share of revenues from oil lifted from their region in south-eastern Nigeria. A group of prominent Commonwealth personalities, led by a former Canadian foreign minister, Flora MacDonald, is in Nigeria to prepare a report on human rights conditions for the forthcoming Commonwealth summit in Auckland.
The military government has reacted strongly to statements by British officials, such as Baroness Chalker of Wallasey, suggesting that Nigeria would not be welcome at Auckland unless it announced a timetable for a return to civilian rule. General Abacha has pledged to announce his plans on 1 October.
The announcement of the convictions came a day after the military government unbanned the country's Guardian newspaper, and freed several politicians who appeared before the secret tribunal on charges of coup plotting.
Western diplomatic sources have suggested time is running out for the regime to take action to prevent further isolation. But with British-Nigerian trade worth pounds 500m a year, few analysts believe Britain would do anything more than withdraw its high commissioner.Reuse content