Both the government and union activists in Nigeria are bracing for violence ahead of nationwide protests against the high prices of gasoline. The demonstrations, organized by Nigeria's trade unions, are set to start Wednesday in Lagos.

A spokesman for the opposition All Nigeria People's Party, Ibrahim Modibo, said the government usually reacts with brutal repression to mass demonstrations.

"Whatever we do they will just send the police and the army to use live bullets and weapons against us," said Mr. Modibo. "We are in a kind of state that this is a government of invasion because whatever we try to do they will use force. But the government doesn't listen."

The government, which usually denies permits for such demonstrations for fear of violence, has permitted this one. But presidential aide on public affairs, Chief Femi Fani-Kayode, warned demonstrators they will have to behave.

"These protests cannot attract anything that is unlawful," he said. "These protests must not degenerate into violence and intimidation, which has happened in the past. These protests must have the support of security agencies. They must be well organized and so on and so forth within that context. We certainly have no problem with legitimate protest and peaceful protest."

Unions called for the march in Lagos and demonstrations in other cities at later dates to protest higher gasoline prices. The unions had called general strikes in the past to force the government to reverse its decision to phase out gasoline subsidies.

But the strikes, said Nigerian journalist Gilbert da Costa, proved largely ineffective. "The strikes, which tend to drag for a couple of days, tend to hit hard at the poor rather than the government," noted Mr. da Costa. "Most Nigerians who basically have to make a living day by day tend to suffer when the strike is called and subsequently the organized labor and civil society groups have decided that it's time they try other options."

Union, opposition and civil society leaders say they also hope to launch a movement against government corruption and widespread poverty.