Investigators believe terror mastermind Abu Musab al-Zarqawi (search) used a Swiss-based cellular phone to communicate with Muslim extremists worldwide before the Iraq war, a newspaper reported Thursday.

The Geneva daily Le Temps said it had seen a copy of a confidential report by the Federal Police Office saying the Jordanian militant used a Swiss Subscriber Identity Module (search), or SIM card, in his phone to stay in touch with individuals in Europe, as well as Hong Kong and Chile.

Just before the Iraq war — which began with the March 2003 U.S. invasion — Swiss investigators traced al-Zarqawi to Syria by tracking his calls, according to the newspaper. It said he stopped using the card in spring 2003.

Daniele Bersier, a spokeswoman for the Federal Police Office, declined to comment.

Al-Zarqawi's Al Qaeda-linked movement has claimed responsibility for many of the bombings and beheadings of foreign hostages in Iraq. It is believed to have used the city of Fallujah as a headquarters, although U.S. forces recently cleared the city of most insurgents.

Swiss authorities previously have said they tracked senior Islamic militants through their cell phone cards, but have refused to confirm their names.

Le Temps said investigators cite three prominent militants now in U.S. custody as having been traced and captured through their use of cellular phones, including:

Khalid Shaikh Mohammed (search), the alleged Sept. 11 mastermind and No. 3 Al Qaeda (search) leader, who was captured in March 2003 in Pakistan.

— Abd al-Rahim al-Nashiri, who is believed to have hatched the attack on the USS Cole (search) four years ago in Yemen that killed 17 American sailors. In September, a Yemeni court sentenced him to death in his absence for the Cole attack.

— Abu Zubair al-Haili, the Al Qaeda operational chief who allegedly helped the terror group's foot soldiers escape from Afghanistan during the U.S.-led war there in 2001. He was caught in June 2002 in Morocco.

The police report did not say where or when the terrorists' cards were purchased, Le Temps noted. Al-Zarqawi used a version sold only from 1999-2003, it said.

A SIM card is the thumbnail-sized chip that fits inside a cell phone, allocating a number to the phone. The prepaid versions include an amount of calling time, which can be replenished easily with top-up cards.

When a person makes or receives a call with the phone outside Switzerland, computers record the calling and receiving numbers and the cell phone user's location. Swiss investigators can obtain the data if they open a formal criminal inquiry.

Last year, Swiss lawmakers closed a legal loophole that allowed customers to purchase SIM cards anonymously. That change came into force in August.

In January, Swiss police discovered 300 SIM cards at the home of a suspect captured in a sweep on an alleged Al Qaeda support network that investigators say supplied fake documents to enable collaborators to enter Switzerland and other European countries.

The alleged Swiss-based gang is suspected of ties to terrorists behind a series of attacks on foreigners' residential compounds in Riyadh, Saudi Arabia, in May 2003. The bombings killed 34 people.

Cell phones seized from terror suspects in Saudi Arabia were found to contain several Swiss numbers, which investigators here have tied to the men seized in the sweep in Switzerland.

Earlier this year, Swiss authorities said investigators concluded that Switzerland was likely used as a base for the financing and logistical support of Al Qaeda, although it was not a hub for the terror group.