MEXICO CITY, April 5 (Reuters) - Mexico must do more to resolve who was responsible for the deaths and disappearances of hundreds of students and political activists in the 1960s and 1970s, a U.S. human rights group said on Thursday.
Last week, a special prosecutor's office set up to look into political torture, kidnappings and murders by former government officials closed down after failing over five years to send a single person to jail.
"The special prosecutor's office may be gone but the need to address the legacy of past abuses remains," said Jose Miguel Vivanco, Americas director for Washington-based Human Rights Watch.
"Mexico must still find a way to meet its obligation to investigate and prosecute these cases."
Security forces and senior government officials from the Institutional Revolutionary Party, which ruled Mexico for seven decades, crushed leftist student and guerrilla movements in a "dirty war" in the 1960s and 1970s.
Attempts to convict former President Luis Echeverria for involvement in a 1968 massacre of leftist students just days before the Olympic Games in Mexico City have foundered, although efforts officially continue.
Echeverria was interior minister when security forces stormed a student rally in a square in the capital's Tlatelolco district. Two years later, he became president.
Officials say about 30 people died in the 1968 killing, although witnesses and rights activists put the toll as high as 300.
The special prosecutor's office began to wrap up at the end of former President Vicente Fox's term in late November and its closure became official last week.
President Felipe Calderon, who took office in December, has said little about plans to investigate the decades-old rights abuses.
He has used the army and elite police to wage a war against violent drug gangs in several states, raising concerns among some critics about possible human rights violations.
Other Latin American countries have managed to make former officials accountable for human rights crimes despite amnesty laws impeding actual convictions, Human Rights Watch said in a statement.
"While other countries, such as Argentina, Chile and Uruguay, are now making real advances in prosecuting past abuses, Mexico remains unwilling to do so," said Vivanco.
A report published last year by Mexico's special prosecutor accused three former presidents, including Echeverria, of overseeing systematic violence.