MADRID, Spain (CNN) -- The Basque separatist group ETA warned on Friday that its violent 40-year-fight for Basque independence "will continue" if the Spanish government doesn't offer "an adequate response to the root of the problem."
Interior Minister Alfredo Perez Rubalcaba believes ETA remains dangerous despite recent arrests.
The warning came in an ETA statement published in the Basque newspaper Gara, just 10 days after police arrested the group's suspected leader in France. Five other suspected ETA operatives were arrested in France and Spain as well.
In the statement, ETA also claimed responsibility for four recent attacks, including the car bomb explosion at a Civil Guard barracks in northern Spain earlier this month which killed a guard member and wounded four others.
ETA is blamed for more than 800 deaths and thousands of injuries during its violent campaign since 1968. The European Union and the U.S. list ETA as a terrorist group.
The latest ETA statement is unlikely to be a surprise to the Spanish government, which had no immediate comment. But earlier this week, Interior Minister Alfredo Perez Rubalcaba, speaking in Spanish parliament, said that ETA remained dangerous despite the recent arrests.
ETA could quickly regroup, and had already named its top new operatives, Rubalcaba said.
If the government "does not give an adequate response to the root of the problem, the conflict will continue and we will be obliged to keep fighting as we have until now," ETA said in its statement in Gara, a Basque newspaper where it typically publishes policy statements and claims of responsibility for attacks.
Spanish officials said the arrest last week of the suspected ETA leader, Francisco Javier Lopez Pena, was a big blow to the group. He was picked up May 20 at an apartment in central Bordeaux with three others. Police later arrested a fifth suspect in France, and a sixth suspect in Spain.
Analysts say police consider Lopez Pena to have been among ETA "hard-liners" who wanted to come out fighting from ETA's unilateral cease-fire declared in March 2006. That cease-fire, declared at a time when ETA had been on the defensive after a string of arrests, raised hopes for an end to four decades of separatist violence.
But then an ETA bomb at Madrid's airport in December 2006 -- during the cease-fire -- killed two men and caused heavy damage. Police suspect that Lopez Pena, 49, had a hand in that attack.
After the airport bombing, the government considered the fledging peace process over, but ETA did not officially end its cease-fire until June 2007. Since then authorities have blamed ETA for four deaths, including the guard officer killed earlier this month.
ETA has traditionally used southern France, just north of Spain's Basque region, as a rear-guard logistics base. But in recent years, increased French and Spanish police cooperation has made it more difficult for ETA operatives.
There are about 500 ETA convicts or suspects in Spanish jails and more than 100 more in French jails, authorities have told CNN.