Uganda was on high alert Friday over fears of an attack similar to the bloody mall assault by Somalia's Shebaab fighters in neighboring Kenya, where investigators continue to recover charred body parts.
At least 67 people were massacred in the upmarket Westgate shopping centre in Nairobi when gunmen stormed the crowded complex on Sept. 21, firing from the hip and hurling grenades at shoppers and staff.
On Thursday, investigators found a charred skull in the wreckage of the mall, Kenyan police said, adding that DNA testing would be carried out to help identify it. Automatic rifles were also found.
The Kenya Red Cross lists 23 people as missing a month after the siege.
Fears are high the Shebaab will follow through on their threat to launch further attacks, with the Al Qaeda linked extremists this week bragging in propaganda posters at rallies in Somalia that "Westgate was just the beginning."
"Stay alert and watch each other's steps and activities, as we are still threatened by terror," the Ugandan police said in a message, as armed security forces patrolled outside shopping centres in the capital Kampala.
It followed a message Tuesday from the US embassy in Uganda which said it was continuing "to assess reports that a Westgate-style attack may soon occur in Kampala."
The embassy said there was no further information on the timing or location of any attack.
Shebaab insurgents claimed the Westgate attack, saying it was in revenge for Kenya military action against the group in southern Somalia.
Uganda also has troops in Somalia with the African Union force that is battling the Shebaab, and has been attacked on home soil by the extremists before, in 2010 bomb blasts that killed 76 people.
The warnings come as a Norwegian citizen of Somali origin was reported to be suspected of being one of the attackers who stormed the Westgate.
The 23-year-old was named by the BBC as Hassan Abdi Dhuhulow.
Dhuhulow was born in Somalia, but he and his family moved to Norway as refugees in 1999, according to relatives who spoke to the BBC.
However, other relatives denied it was Dhuhulow who appeared in security camera footage of the attack.
Norway's PST intelligence agency last week launched a probe after it obtained information about the possible involvement of a Norwegian of Somali origin in both planning and carrying out the attack.
However, on Friday it said that "at this point, we do not wish to confirm or deny this claim."
Norwegian investigators have been sent to Nairobi to work with their Kenyan counterparts.
"It has not yet been determined whether a named Norwegian citizen actually took part in the attack or not," the PST agency added.
"Based on the information that we have uncovered this far in the investigation, however, the suspicion of his involvement has been strengthened."
Witnesses in the mall described how the fighters stormed the complex around midday on September 21 when it was crowded with shoppers.
The gunmen coldly executed scores of people, with witnesses recounting how in some cases they called out to those wounded, then finished them off at close range.
The siege was declared over four days later.
Kenya's security forces were initially praised for bravery in battling the insurgents, but were later heavily criticised after shopkeepers entering the mall after the siege said their stores had been systematically looted.
A propaganda video released this week by the Shebaab praised foreign fighters, showing several insurgents it said had come from Britain and who had been killed in battle.
The video was apparently made before the Westgate attack as it made no reference to it, although it highlights the "suffering of Muslims in Kenya" as well as other countries.
The film, narrated by a man in a military jacket, face hooded in a black mask and speaking with an apparently British accent, claims fighters from multiple nations including Ethiopia, Eritrea, Lebanon, India and Pakistan had all fought with the force.