Birtukan Medeksa is seen by some as a national heroine
The main opposition parties in Ethiopia have held a march in Addis Ababa to call for the release of their imprisoned leader, Birtukan Medeksa.
The demonstrators handed in a petition to the authorities about Ms Birtukan.
She is serving a life sentence, after officials revoked a pardon which had previously seen her set free.
Ethiopia has very little tradition of public protest, the BBC's Elizabeth Blunt in Addis Ababa says, and passers-by stopped and stared in amazement.
Almaz GebreEgziabher, Ms Birtukan's mother, hopes the demonstration may help her daughter be released in time for the Ethiopian Easter this weekend.
"I am happy. I saw her last Saturday, and she is quite well. But I am praying that, with the help of God, she might be released tomorrow or the day after so that she can spend Easter with me and her daughter," she said.
Ms Birtukan's five-year-old daughter and mother are the only people who are being allowed to visit her in jail.
She was among more than 100 people jailed for political offences after Ethiopia's election in 2005, most of whom have since been pardoned.
At the time of her re-arrest her colleague Berhanu Nega, who was also pardoned and now lives in exile, told the BBC it showed the government "was hell-bent on staying in power".
Ms Birtukan is a former judge and was one of the younger and more charismatic leaders of the coalition which did well against the ruling party in the 2005 elections.
Our correspondent says that while in jail facing charges of treason, she became even more of a heroine, attracting widespread sympathy as a single mother separated from her baby daughter.
After the opposition leaders were pardoned and released last year, she emerged as the leader of a new coalition, the Union for Democracy and Justice (UDJ), painstakingly stitched together from various opposition groupings to contest elections in 2010.
The government news agency, quoting the ministry of justice, said her pardon had been revoked because she had denied requesting her pardon.
Ms Birtukan's problems started when she spoke to journalists abroad about the way the opposition leaders were released, our correspondent says.
She talked about negotiations which had taken place between the opposition and government, with the help of a panel of elders, before their pardon was granted.
The government prefers to lay emphasis on a document signed by the prisoners, regretting any mistakes they had committed and asking for pardon.
This implies that their release was part of a normal judicial process, rather than in any way part of a negotiated political deal.