Spain (search) held a nationally televised funeral Tuesday for seven intelligence agents slain in Iraq amid suspicions that contacts in Iraq working with the agents tipped off their killers.

Prime Minister Jose Maria Aznar (search) -- one of President Bush's strongest backers in the Iraq war -- vowed not to withdraw Spain's 1,300 troops after his country suffered its deadliest attack in Iraq.

In Saturday's attack, eight Spaniards were returning from Baghdad (search) to the Spanish base in Diwaniyah when they were ambushed by gunmen on a road 18 miles south of the Iraqi capital. One agent survived.

The group of Spaniards -- four agents due to return home and four others replacing them -- had gone to Baghdad apparently so the new agents could meet "information sources," the newspaper El Pais reported Tuesday, quoting sources in Spain's National Intelligence Center.

Defense Minister Federico Trillo said the attack probably was linked to the October shooting of Spanish intelligence agent Jose Antonio Bernal. In that attack, the gunnmen knew where Bernal lived in Baghdad. The assailants knocked on the front door of his house and killed him as he ran down the street trying to flee.

"So there may have been a tip-off or betrayal by someone in that community, which is never entirely controllable," Trillo told Spanish National Radio on Monday, apparently referring to Iraqis who worked with or knew the Spaniards.

Spain had received several threats prior to Saturday's attack and the agents knew their trip was risky, Trillo said.

News reports said the Defense Ministry's suspicion of a betrayal was fueled by the fact that the agents made last-minute changes Saturday, beginning their journey earlier and taking a different route than planned.

The daily El Mundo cited evidence given by the survivor of the attack, Jose Manuel Sanchez Riera, that the agents had been traveling in two vehicles and came under fire from a car behind them. During the shootout, the agents were also attacked from a nearby settlement.

The attack was the worst suffered by Spain in Iraq. So far Spain has lost 10 men there.

Aznar vowed to not withdraw the country's 1,300 troops stationed in south-central Iraq. Aznar went before a special session of parliament Tuesday to reaffirm his commitment, saying retreat "can never be an option in the face of terror."

Aznar began his speech to parliament by reading out the names of the seven agents, drawing applause.

Spain lowered its flags to half staff Tuesday as seven coffins were taken from the Defense Ministry's military hospital to the Madrid headquarters of the National Intelligence Center, where a nationally televised funeral service was held at midday.

Dozens of bereaved family members received the condolences of King Juan Carlos, Queen Sofia and Prince Felipe, Aznar, members of his cabinet and many high-ranking politicians.

Like Bernal, the agents were decorated posthumously with the Official Cross of the Order of Civil Merit.

Speaking to parliament, Aznar commended the agents' work, saying they took cover during the attack and shot back, acting "with proper firmness." He said the agents were involved in counter-intelligence and counter-terrorism operations aimed at protecting Spanish forces.

Lt. Col. Jose Luis Gutierrez, the head of Spanish military operations in the Iraqi province of Najaf, told El Pais that the loss dealt a severe blow to Spain's intelligence service in Iraq and left Spanish troops there vulnerable.

"Without them, we are left blind," he said.