Nine Catalan independence activists have been arrested in Barcelona and face charges of “rebellion, terrorism and possession of explosives”, authorities have said.

Police said they confiscated material they alleged could be used in bomb making during raids early on Monday morning. The raids were aimed at aborting actions that “could have caused irreparable damages”, prosecutors said.

According to the police, those detained are associated with the Committees for the Defence of the Republic (CDR), a network of radical groups that advocates direct action to secure Catalan independence from Spain.

The arrests, made in a variety of locations in the Barcelona area, were carried out by the civil guard under instruction from an audiencia nacional (national court) judge, who deals with serious offences such as terrorism, drug smuggling and organised crime.

The nine arrested people are said to be members of the CDR’s so-called tactical response team. The team has previously blocked major roads and railway lines but its principal tactic to date has been passive resistance rather than outright confrontation.

Police said they believed the activists were planning to carry out sabotage and violent attacks on 1 October, the second anniversary of the illegal referendum on independence, to coincide with the sentencing of Catalan politicians for their role in the poll and the subsequent unilateral declaration of independence. The politicians are expected to be sentenced on or around 10 October.

The arrests were the result of an anti-terrorist investigation that was launched more than a year ago.

Catalan separatists are increasingly divided on how to maintain the impetus of a movement that is gradually losing momentum, with one section calling for dialogue while the other, led by the former Catalan president Carles Puigdemont and his successor, Quim Torra, calling for “confrontation” with Madrid.

The two main grassroots independence organisations, the Catalan National Assembly and Òmnium Cultural, believe direct action would damage the movement’s image, while the CDR has called for active civil disobedience, claiming “liberation doesn’t exist without tension”.

Last year, on the first anniversary of the referendum, Torra was widely criticised for inciting the CDR to cause maximum disruption. The radicals have since turned on the president, claiming he is a traitor to the cause.

In a tweet, the CDR responded to the arrests with a call for a “united front” against the “kingdom of Spain’s machinery and repressive forces”, adding: “Nothing can stop a committed and combative people.”

Torra said Spain was trying to construct a violent narrative ahead of the sentencing date for the Catalan politicians, several of whom are accused of rebellion, a charge that will only stick if it can be proved that they used violence. The independence movement “is and always will be peaceful”, he said.

Puigdemont accused Spain of “fabricating a terrorism case”, adding: “Freedom is the way to respond to repression.”