Eta said it had killed 758 people in its decades-long campaign for independence and admitted carrying out two attacks for which it had never previously claimed responsibility, a newspaper that was once the Basque separatist group’s mouthpiece has revealed.

Basque daily Gara published excerpts on Tuesday of the bulletin the group released in April before it disbanded in May, marking the end of western Europe’s last armed insurgency. It was the group’s last internal newsletter before it dissolved.

The newsletter said Eta had killed a total of 758 people since it emerged in 1959 – less than the 853 deaths attributed to the armed group by the Spanish government. It added that among its victims were more than 320 civil guards and police agents, and 101 military personnel, according to Gara.

One of the two attacks it had never previously admitted to was an explosion in a Madrid cafeteria in 1974 that left 13 people dead. According to the newsletter, Eta carried out just over 2,600 armed actions in total.

Publication of the excerpts drew strong criticism from victims’ group Covite. In a statement, it said they showed Eta had disbanded “without repudiating its criminal trajectory nor condemning a totalitarian and discriminatory political project they tried to impose by force”.

In one assertion that drew criticism, Eta said the 1968 assassination of Melitón Manzanas, a high-ranking police officer under the Franco regime, who was known as a torturer, was its first. But historians say civil guard agent José Antonio Pardines was actually the first to be killed by the group, earlier that year.

In its newsletter as quoted by Gara, Eta also lauded its actions against a planned nuclear power plant in the Basque town of Lemoiz, which was deeply unpopular and was eventually dropped.

The Basque group targeted workers at the plant, such as its production manager, Jose Maria Ryan, a 39-year-old father of five. Eta kidnapped him in January 1981, giving authorities a seven-day ultimatum to stop construction, and eventually executed him with a bullet to the head.

“Lemoiz showed the efficiency of the armed struggle in the eyes of wide sections of society,” Gara quotes Eta’s bulletin as saying.

It is unclear whether Eta’s killings or Basque society’s general opposition to the plant eventually led authorities to cease construction.

In the bulletin, Eta also condemned its 1987 attack on a supermarket in Barcelona – its deadliest, resulting in 21 deaths – as “the worst mistake and tragedy”.