He is also is seeking the arrest of former interior minister Mario Moya Palencia, former attorney-generals Julio Sánchez Vargas and Pedro Ojeda Paullada, and other former high-level officials from that era, who he has charged with ''genocide''.

On Jun. 10, 1971, a group of paramilitaries known as 'Los Halcones' (the Hawks), allegedly created by the Institutional Revolutionary Party (PRI) -- which ruled the country from 1929 to 2000 -- attacked a student demonstration in Mexico City.

According to the authorities, 30 people were killed. But independent sources put the number at over 100. Dozens were injured.

Ibarra said ''They say they are really going to bring people to justice, but we don't believe it now, because everything they have said in the past few years has turned out to be a sham.''

She pointed out that former security officials and members of the military implicated in the repression of dissidents opposed to the PRI governments in the 1970s who have been arrested and prosecuted in recent years are now free.

At least 500 dissidents -- mainly student activists and members of armed guerrilla groups opposed to the government -- became the victims of forced disappearance in the late 1960s and the 1970s.

One of the ''disappeared'' was Ibarra's son Jesús Piedra Ibarra, who authorities claim was killed in a shoot-out with the police. But according to the testimony of survivors of the repression, Piedra Ibarra was seen alive in several different clandestine jails after his supposed death.

''We do not have any hope of the justice that the people of Mexico are demanding,'' said Ibarra. ''These showy publicity stunts don't convince us. We have been on the receiving end of deceptions and hoaxes for 30 years.''

The request for the arrest of Echeverría and other former officials should have come long ago, she said, adding ''We hope they live up to their duty now.''

''But if Echeverría is arrested, they'll say it's a historic event. Well I don't know why a case of justice would be a historic event,'' said Ibarra.

Activist Alejandra Ancheita with the Miguel Agustín Pro Juárez Human Rights Centre was more optimistic, telling IPS that the request for the arrests is ''absolutely'' historic.

Referring to the investigation by the special prosecutor, she said ''it seems to have been one of the most thorough prior investigations,'' establishing a solid foundation for the arrest of the suspects.

On Oct. 2, 1968, Echeverría, who is now 82, was minister of the interior when the army was called out to put down a student protest in Tlatelolco square in the capital.

The huge demonstration was the culmination of a period of effervescence in the university movement.

A paramilitary group known as the 'Olympic Battalion' and the military surrounded the square and opened fire on the demonstrators.

No Mexican government has ever recognised that 300 people died that day -- the figure provided by the families, survivors and human rights organisations.

After seven decades in power, the PRI was defeated by President Vicente Fox's centre-right National Action Party (PAN) in 2000.

In November 2001, Fox created the special prosecutor's office, charged with investigating the 1968 and 1971 massacres and other cases of repression, and bringing those responsible to justice.

In July 2002 Echeverría gave his testimony to the special prosecutor's office in connection with cases of genocide, homicide, and forced disappearance.

During the six-hour deposition, the former president maintained that he was innocent of all charges. His defence attorneys also argue that the statute of limitations has already run out on the crimes of which he is accused.

Furthermore, Juan Velásquez, one of Echeverría's lawyers, maintains that there has been no ''genocide'' in Mexico, and says the paramilitary group ''was created by the late former president Gustavo Díaz Ordaz (1964-1970), who years later assumed all responsibility for what occurred on Oct. 2, 1968.''

Velásquez added that what happened in June 1971 was a firefight between the Hawks and a group of protesters. But photos show that the students were attacked by the paramilitaries, with bamboo rods at first, and then with shots from revolvers and machine guns.