French authorities arrested four more people Wednesday morning in a round-up of suspected terrorists believed to have been plotting attacks in Iraq.

The arrests followed the detention Monday of six others who authorities believe were preparing assaults on U.S. forces in Iraq (search). It was the first operation of its kind by the French government since reports surfaced last year that French citizens or residents were joining the insurgent ranks.

The justice minister suggested the roundup was timed to allow France's domestic counterterrorism agency, known as the DST, to gather better information.

"The anti-terrorist struggle is a daily war," Justice Minister Dominique Perben, said on France-2 television. "It is a meticulous job to work back up the networks, to draw connections between names, between types of behavior and methods of action."

Under French law, those arrested in the investigation can be held for up to four days before being released or facing preliminary charges.

Perben gave no details about the arrests. But he said France's six magistrates with sweeping powers to combat terrorism "follow step-by-step a certain number of suspects, a certain number of people who are susceptible of being in contact with terrorist groups in France or overseas."

Other arrests have been made throughout Europe (search) – including two detained in Germany on Sunday – of others heading to Iraq.

On Sept. 22, judicial authorities opened an investigation to determine whether a network for sending Islamic combatants to Iraq exists in France.

The investigation was opened after the bodies of several French were discovered in recent months in Iraq.

Experts here have said in the past that they do not believe there is a substantial France-based network to help Muslim (search) extremists make their way to Iraq to fight U.S.-led multinational forces there.

However, there have been numerous arrests of suspected al-Qaida-linked cells in France. Six people are on trial in Paris in connection with an alleged al-Qaida inspired plot to bomb the U.S. Embassy here.

In neighboring Germany, numerous arrests linked to Iraq have been made recently. On Sunday, German security forces arrested two alleged al-Qaida members, an Iraqi and a Palestinian, accused of plotting an attack in Iraq. Earlier this month, German police arrested 22 people to break up an alleged network of Muslim extremists suspected of falsifying passports and spreading militant Islamic propaganda.

The Associated Press contributed to this report.