NAIROBI, Kenya -- Only days after heavily-armed assailants stormed a crowded mall and killed scores of people in the capital, militants killed three people near the border with Somalia, Kenyan officials said Thursday, putting this country even further on edge.
According to Kenyan police officials, there were two attacks, the first Wednesday night on a group of police officers on a foot patrol in Wajir in which a bystander was killed. Militants struck again early on Thursday, raiding a police camp in Mandera, killing two police officers and setting fire to a dozen vehicles.
The Kenyan authorities immediately blamed the Shabab, the Somali militant group that has claimed responsibility for killing more than 60 shoppers in the mall.
Rono Bunei, the Mandera police commander, said the attack in Mandera was under investigation, "but obviously it leads to suggest that either the al Shabab or their sympathizers are responsible."
He said that his area had been relatively quiet for the past couple of months, though there have been small-scale attacks along the border by militants from Somalia for years, including brazen kidnappings of tourists and aid workers.
As flags flew at half-staff across the country for a three-day period of mourning, the investigation into the massacre at the upscale Westgate mall in Nairobi was moving slowly. Video footage released by the Kenyan military showed a gaping crater where a section of the mall's parking lot had crumbled, sending vehicles tumbling into an enormous, smoking pit. Many cars had been burned down to paint-less skeletons.
Dozens of Western investigators, including a large F.B.I. contingent, have flown into Nairobi in the past few days, and there were fears that the mall may be booby-trapped with explosives.
A remote-controlled police robot scooted room to room, checking for bombs on Thursday. Several loose grenades were discovered, a Western official said, and investigators were especially interested in any clues that would reveal whether all the attackers had been killed in the mall or if some had escaped, as several witnesses claimed.
"The cordon around the place was not that great," said one Western official who was not authorized to speak publicly. "I'm not sure the Kenyans were organized enough to lock it down."
Several witnesses said that one attacker was a Caucasian woman who slipped out of the mall after instructing other assailants whom to shoot. Kenyan officials said that a British woman, Samantha Lewthwaite, who converted to Islam and married a man who became a suicide bomber, might have been involved.
On Thursday, Interpol issued an international arrest notice for Ms. Lewthwaite. The notice, requested by the Kenyan government, did not mention the mall massacre and said that Ms. Lewthwaite has been wanted since 2011 on charges of possessing explosives and conspiracy to commit a felony. In Kenya and Britain, Ms. Lewthwaite is frequently referred to as the "white widow."
Several Western officials said they had heard reports from the Kenyan military that some of the victims in the mall had been beheaded and butchered with knives. Kenyan officials declined to comment, but one Western security adviser, who was not authorized to speak publicly, said "I fully expect it."
"They had people under their control for three days," the adviser said, referring to how the assailants had holed up in the mall with terrified shoppers hiding in several places.
Many Kenyans are now beginning to ask the same question: How could this happened? How could 10 to 15 militants, with military-grade weapons, storm a crowded mall in central Nairobi and start shooting people at will with no organized armed response for several hours, and then manage to hold off the Kenyan army for days?
Mike Sonko, a Kenyan senator, said during a debate in the Senate earlier this week that he had passed on information about such a plot to police and intelligence officials, Kenya's Standard Media reported. Several Twitter messages over the past few days have criticized the way the Kenyan government has handled the crisis. One Kenyan woman wrote that she wished her government "would understand that we are asking questions because we are terrified that will happen again. Obfuscation doesn't help."
But for the most part, unity remained the overriding sentiment, with glowing reports on Kenyan television stations about ordinary citizens donating blood for the wounded and money for the victims' families. The Twitter hashtag #weareone was shorthand for the solidarity the nation has sought in the aftermath of the deadly attack.
The attackers gunned down several children, including a girl who had attended ninth-grade at the International School of Kenya, commonly referred to as I.S.K. An American official said Thursday that during the three-day effort to dislodge the last assailants in the mall, an American security adviser delivered a crate of tear gas to Kenyan soldiers, pulled out a canister and said, "Use this one first, courtesy of the 9th grade of I.S.K."
According to the American official, the Kenyan soldiers lobbed that specific canister into the mall, smoked out one of the assailants and shot him dead.
This article originally appeared in The New York Times.