Armed police and soldiers patrolled Uganda's capital on Wednesday after twin suicide bombings claimed by the Islamic State group killed four people, the latest in a string of attacks in the East African country.
Checkpoints have been set up on several roads in Kampala, while the areas where the two bombings occurred in the heart of the capital have been closed off to motorists as teams of investigators scour the blast sites.
"We encourage the public to remain on high alert as threats are real and high," Kampala Metropolitan police spokesman Luke Owoyesigyire told AFP, announcing stepped up security measures.
US Secretary of State Antony Blinken, on a visit to neighbouring Kenya, said the bombings highlighted the need to improve security across the region.
Tuesday's attacks occurred within minutes of each other, with two suicide bombers on motorbikes disguised as "boda boda" motorcycle taxi drivers detonating a device near parliament, while a third attacker targeted a checkpoint near the central police station.
Ugandan police had initially said they were the work of "domestic terrorists" linked to the Allied Democratic Forces (ADF), an armed group active in eastern Democratic Republic of Congo.
They followed two attacks last month also blamed by Kampala on the ADF, which the United States has linked to the IS group.
"The attack yesterday was a painful reminder of our vital reason why we continue to work together to improve security across the East African region," Blinken told reporters in Nairobi.
Kenya itself has also beefed up security in towns and border areas following the blasts.
Ugandan police said Tuesday three people had died in the attacks. Baterana Byaruhanga, executive director of Mulago National Referral hospital, told reporters Wednesday a fourth victim died overnight from his injuries.
Military police were guarding entrances to the sprawling medical facility, which was treating victims, many of them police.
"I did not go to work in the market today because of the attacks yesterday," 31-year-old mother of two Sylvia Nabukeera, who works in Kampala's commercial hub Kikuubo, told AFP.
"I have temporarily suspended work to take care of my kids until it is safe to go to work."
'Focusing on Uganda'
Investigations were ongoing into the blasts, with police hunting for suspects, after foiling a third bombing on Tuesday and shooting dead the attacker.
Ugandan police last month arrested a number of alleged ADF operatives and warned that extremists were believed to be plotting a new attack on "major installations".
The arrests followed a bus explosion near Kampala that wounded many people and a bombing at a roadside eatery in the capital that killed one woman.
Uganda also blamed the ADF for a foiled attack in August on the funeral of an army commander who led a major offensive against Al-Shabaab militants in Somalia.
Washington in March linked the ADF to IS, which in 2019 began to claim some ADF attacks on social media, presenting the group as its regional branch -- the Islamic State Central Africa Province, or ISCAP.
The ADF, historically a Ugandan rebel group, has been accused of killing thousands of civilians in eastern DRC.
"It's increasingly clear that the ADF is refocusing its attention on Uganda," said Kristof Titeca, an expert on the group at the University of Antwerp.
"It may link with an increased influence of jihadist elements within the ADF in the last couple of years," he told AFP.
Experts consider the ADF to be the bloodiest of more than 120 armed groups that roam eastern DRC, many of them a legacy of two regional wars a quarter of a century ago.
In 2010, twin bombings in Kampala targeting fans watching the World Cup final left 76 people dead, with Al-Shabaab claiming responsibility.
The attack was seen as revenge for Uganda sending troops to Somalia as part of an African Union mission to confront Al-Shabaab.