UNITED NATIONS — The Security Council yesterday labeled the assassination of a former Pakistani prime minister, Benazir Bhutto, a “terrorist suicide attack” and condemned it “in the strongest terms,” but diplomats were very careful not to pin the attack to a perpetrator.

Diplomats who rushed in from a week-long year-end vacation declined to address on the record the many speculations and theories about the assassination and its possible perpetrators. While most diplomats theorized that it must have been the work of Al Qaeda, others said elements within Pakistan’s intelligence services, military, or even the government, may have had an interest in the chaos that ensued.

One diplomat, who spoke on condition of anonymity, pointed to the previously unknown mode of operation — a gunshot to Ms. Bhutto’s neck before the perpetrator blew himself up — as proof that a much more professional hand than the known terrorist groups was involved.

Officially, however, all diplomats condemned terrorism while saying they were in the dark about who the terrorists were.

“Pakistan itself remains a victim of terrorism,” a Pakistani ambassador to the United Nations, Farukh Amil, said. “Our president, our former prime minister, and ministers have been attacked. These terrorists are targeting all forces of modernism. However, the government of Pakistan remains absolutely committed to fighting terrorism in all its forms and manifestations.”

But when asked about claims of responsibility by Al Qaeda-affiliated groups, Mr. Amil said his government has not yet determined who is responsible. “Many people can claim many things, but right now it’s too early to say,” he said. The council quickly agreed on a statement that condemned “the terrorist suicide attack by extremists” and called on all Pakistanis to “exercise restraint and maintain stability in the country.” It also called to bring the assassination’s “perpetrators, organizers, financiers, and sponsors” to justice, urging cooperation from all countries.

Although the General Assembly has failed to agree on the definition of terror, the council has in the wake of the September 11, 2001, attacks, passed several resolutions that outlawed Al Qaeda, the Taliban, and their affiliates. U.N. Members became cautious after — under pressure from the Spanish government, the council agreed to condemn a Basque group for the March 11, 2004, Madrid bombing, which later was proved to be the work of Al Qaeda. Russia’s U.N. ambassador, Vitaly Churkin, told The New York Sun that yesterday’s statement condemned a terrorist act, “but who exactly did it, and for what political purpose, we don’t know.” In addition, America’s U.N. ambassador, Zalmay Khalilzad, said yesterday was “not a good day.” “I knew Benazir Bhutto quite well,” he added. “She is a friend of mine, and I was very saddened by the news.”

Bhutto’s “death is a loss for the cause of moderation, democracy, and rule of law for Pakistan,” he said. “She was clear-headed about the problems of her country, the challenges that she faced — even the security challenges she faced.” Secretary-General Ban, who attended yesterday’s council session, also paid tribute to Bhutto, saying he extended his “deepest condolences to the families of Mrs. Bhutto, her colleagues, supporters, and people and government of Pakistan, while urging calm and restraint.”