The latest successful police measures have considerably weakened the armed Basque separatist group ETA in France, French Prime Minister Francois Fillon said Friday, according to dpa. Speaking in Madrid where he met his Spanish counterpart Jose Luis Rodriquez Zapatero, he said ETA's infrastructure in southern France was much weaker. Both countries stressed their determination to continue their battle against terrorism. French policed detained Thursday Juan Cruz Maiza Artola alias Lohi, 56, ETA's logistics chief, and two other suspected activists in Rodez in the south-west. Police were searching the flat where they were held. Maiza Artola had been sentenced in absentia to nine years in prison by a French court. The other two detainees were identified as Iker Iparraguirre Galagarra, one of the ETA members most wanted by Spain, and as Galder Biotz Cornago. Since ETA ended its 14-month ceasefire on June 6, Spanish and French police have subjected the group to constant crackdowns. Eighteen ETA suspects have been detained in France, Spain, Mexico and Canada. Zapatero has warned of more ETA attacks, the danger of which should not be underestimated. "We live with a terrorist threat which means risk. We must all be aware of this," he noted. ETA is blamed for more than 800 deaths in its armed campaign since 1968 for a sovereign Basque state.