Madrid, Spain (CNN) -- Police arrested four of the "most-wanted" suspected members of the Basque separatist group ETA overnight in France and Portugal, including one who stole a police car to try to escape, Spain's Interior Ministry said Sunday in a statement.
The first of the operations against ETA started late Saturday when Spanish Civil Guards in the village of Bermillo de Sayago, near the Portuguese border, stopped a man driving a suspicious van, the statement said.
The van contained explosives, weapons and documentation, and while Civil Guards were checking it, the man stole a police car and fled to nearby Portugal.
Spanish authorities immediately contacted Portuguese police, who quickly arrested the suspect in the stolen patrol car.
Soon after, Portuguese police arrested a woman, driving a sedan, suspected of having been ETA's go-ahead "lookout" for the van with explosives, the statement said.
At about the same time, in a forest near the town of Chadrat in central France, police arrested two other ETA suspects, also a man and a woman.
They were detained after they removed 2,000 euros (nearly $2,900) in cash from an ETA hideout which the police recently discovered and have been monitoring. The suspects were armed and the cash was presumably to finance ETA attacks, the statement said.
ETA is blamed for more than 800 deaths in its long fight for Basque independence and is listed as a terrorist group by Spain, the European Union and the United States.
Spain's Interior Minister, Alfredo Perez Rubalcaba, less than two weeks ago issued an unusual public warning that ETA could be a planning a major attack or a high-profile kidnapping, and the government raised its nationwide terrorism alert to "level two."
On Sunday after the latest arrests, Rubalcaba told a nationally-televised news conference in Madrid, "We know what ETA is doing. The message to ETA is, when you go to a hideout or are on a highway, the police will be looking for you, until this is over."
ETA, founded in 1959, is an acronym for Euskadi ta Askatasuna, which means "Basque Homeland and Liberty" in the Basque language.
The vehicle stop in the Spanish village near Portugal was the result of security forces being on "level two" terrorism alert, the statement said.
The level two alert "implies a probable risk of a terrorist attack," the Interior Ministry said, and calls for increased police scrutiny at transit hubs and other public places.
The highest alert is level four, when armed forces are deployed against an imminent threat of attack, an Interior Ministry spokeswoman said earlier.
A ministry statement in December said the alert was raised to level two after reviewing police intelligence, for various reasons: the Christmas holiday season, Spain's role as the rotating European Union president for the first half of 2010, and the "persistent international terrorist threat seen in incidents like the flight from Amsterdam to the United States."
A man has been charged with trying to blow up an airliner en route from Amsterdam to Detroit, Michigan, on Christmas Day. The explosives failed to detonate.
Police last year arrested about 70 ETA suspects in Spain and France, ETA's traditional rearguard base just across the border, officials said.
That includes the arrest in October 2009 of a suspected top ETA leader, the fifth time since May 2008 that a suspected ETA chief operative has been detained.
The four arrests late Saturday in France and Portugal are in addition to two other ETA suspects detained in recent days in northern Spain and southwest France.
Rubalcaba said in a Basque radio interview on December 29 that "ETA is in a weak situation. It's been hit hard by the police and the courts. It's isolated socially, and has infighting in its ranks. In these circumstances, it's easy to predict that ETA is thinking of demonstrating that it's alive, that it exists."