UNITED NATIONS — United Nations officials are astounded at the behavior of top Algerian government officials, who claim to have learned in the spring that U.N. facilities in their country had been designated as targets by North Africa’s fiercest terrorist organization, but failed to pass that information to the U.N.’s security authorities before last week’s Algiers bombing.

Several U.N. officials who spoke about the event yesterday stopped short of blaming the Algerian government. But they said that even now it is unclear to them how specific the pre-bombing warning was, and whether the failure to inform the United Nations of the apparent lurking danger was the result of neglect or something else.

Secretary-General Ban was in Algiers yesterday, visiting the site of the December 11 bombing. He vowed to keep the United Nations active in Algeria despite the twin car explosions that killed at least 37 people, including 17 employees of the United Nations.

Mr. Ban’s one-day trip to Algiers was designed to raise morale and show defiance in the face of terrorism, aides said. He told staffers there that the organization would “spare no effort in ensuring that the U.N. provides adequate security for its staff,” including “a communications system that is adequate when an emergency occurs.”

But several U.N. officials and staffers who were angry about the Algerian government highlighted specific statements made by the interior minister, Noureddine Yazid Zerhouni, on the day of the attack last Tuesday. Mere hours after the bombing, Mr. Zarhouni was able to say his government was “certain” that Al Qaeda in the Islamic Maghreb, a terrorist group also known as the Salafist Group for Call and Combat, or GSCP, was behind the attack.

His statement seemed to rely on arrests and interrogations made after a previous car bombing of the government headquarters and a police station in Algiers, in which 33 people were killed in April. Several terrorism suspects were arrested and interrogated at the time. “Based on information gleaned from members of the GSCP arrested by the security services after the April 11 attacks, public buildings like the U.N. headquarters were among the targets of the organization,” Mr. Zarhouni told reporters last Tuesday.

“We had not been informed of that,” a United Nations official who traveled to Algiers after the second bombing told The New York Sun yesterday. Another senior official at the New York headquarters added, “It is not clear to us what degree of specificity” the Algerian information had. Like all of those who spoke on this issue yesterday, the two officials asked for anonymity, citing the circumstances surrounding the security investigation.

Algeria’s U.N. ambassador, Youcef Yousfi, declined to return several phone calls yesterday.

The U.N.’s undersecretary-general for security, Davis Veness, flew to Algiers last week to investigate the security circumstances that led to the bombing and to assess the security situation in its aftermath, and will remain in Algiers for an unspecified time, according to a U.N. spokeswoman.

Among the issues he would have to investigate is the failure to pass the Algerian suspicions along, as well as reports that the government failed to block the street where the bombing occurred.

In August 2003, the U.N. headquarters in Baghdad was blown up, leaving 22 persons dead, including the top official in Iraq, Sergio Vieira de Mello. Only recently did Mr. Ban announce his intention to raise the organization’s presence in Baghdad, which was significantly lowered after the bombing.

According to the secretary-general’s spokeswoman, Michele Montas, who was with Mr. Ban at an international conference on climate change in Bali, Indonesia last week, the secretary-general decided to fly to Algiers immediately upon hearing about the bombing. But security considerations, and the inability to assure his safety, prevented him from going at the time, Ms. Montas said. After the Bali conference was over, and after attending a Monday conference of donors for the Palestinian Arabs in Paris, Mr. Ban arrived yesterday in Algiers.

“We will not be deterred,” Mr. Ban vowed, addressing staffers. “We will go on doing whatever we can to help build a better future for the people of Algeria. Only by carrying on with that mission can we begin to do justice to the memory of the friends we have lost.”