Groups in Nigeria are intensifying pressure on President Umaru Yar'Adua to open a criminal investigation into alleged corrupt deals under his predecessor, Olusegun Obasanjo. The country's two powerful unions organized a protest march in Abuja to drum up support for a probe. For VOA, Gilbert da Costa has more from Abuja.

This week, the Nigeria Labor Congress and the Trades Union Congress joined religious and civil society groups, as well as opposition political parties and students, to ratchet up the pressure on former Nigerian president Olusegun Obasanjo.

In a march that lasted several hours, the protesters called for an investigation into alleged corruption that took place during the Obasanjo administration.

Nigeria Labor Congress chief Abdulwaheed Omar presented a petition to the anti-corruption Economic and Financial Crimes Commission. He characterized corruption as severely damaging to Nigeria.

"We have organized this rally because we believe Nigeria cannot continue with this spate of corruption. Nigerian labor, generally, decided that corruption is the bane of this country and the only way we can move forward as a nation is combating corruption," he said. "Our ultimate demand is that it is not enough to have public hearings and probes. The only thing that will save Nigeria from corruption is the establishment of a judicial commission of enquiry. This is what we want and this is what the Nigerians demand."

Former president Olusegun Obasanjo is scheduled to appear before a parliamentary panel next week to explain why $16 billion in investment in the energy sector failed to end power outages in the country.

The panel found that Mr.Obasanjo awarded $50 million worth of contracts to power companies that did not exist. They also found that two billion dollars worth of energy contracts were awarded by the former president without a bidding process.

Several allegations, ranging from shady oil contracts, sale of government-owned companies and irregular acquisition of property, are also being looked into.

The scandal has dominated the news in Nigeria, prompting angry reactions from most Nigerians.

Mr. Obasanjo stepped down a year ago after presiding over Nigeria's longest ever stretch of uninterrupted civilian rule.

Anti-corruption campaigners have called for President Umaru Yar'Adua to distance himself his predecessor and avoid what could be interpreted as an attempt to pervert the cause of justice.

Mr. Yar'Adua, Obasanjo's hand-picked successor, has denied suggestions that he was shielding the former president from being probed.

Mr. Yar'Adua came to power pledging zero tolerance for corruption, but some say he has sometimes taken an ambivalent attitude toward corruption.

Mr. Obasanjo was jailed in the 1990s following his conviction by a military tribunal for treason, and the protesters departed with a message they will not rest until the former president returns to jail.