Four dead in Al-Shabaab car bomb near Somali capital
The attack was claimed by the Al-Qaeda-linked Islamist militant group Al-Shabaab, which has stepped up its activities in Somalia and neighbouring Kenya in recent weeks.
The bomb struck near the town of Afgoye about 30 kilometres (20 miles) west of the capital, killing four people and wounding several others including several Turkish nationals, said local police officer Abdirahman Adan.
"The blast was huge, it destroyed a container used by the Turkish engineers who work on the Afgoye road construction," said witness Muhidin Yusuf.
"There were police who were guarding the Turkish engineers and several other people gathering near the checkpoint where the temporary shelter is located," said another witness Ahmed Said.
"I saw the dead bodies of several (people) and Turkish workers who were wounded in the blast."
The Islamist group, which has fought for more than a decade to topple the Somali government, has carried out a series of attacks in recent weeks including a massive car bombing in Mogadishu on December 28 that killed 81 people.
That attack, which hit a busy checkpoint in the southwest of the city, was Somalia's deadliest assault in two years.
And on January 5, the jihadists stormed a military base used by US forces in Kenya's coastal Lamu region, killing three Americans.
Last week, Al-Shabaab warned that Kenya will "never be safe", threatening tourists and calling for more attacks on US interests.
Kenya sent troops into Somalia in 2011 as part of an African Union peacekeeping mission fighting against Al-Shabaab, and has seen several brutal retaliation attacks both on its troops in Somalia and civilians in Kenya.
The uptick in attacks comes almost a year since the January 15 siege on an upscale Nairobi hotel which left 21 people dead.
In recent statements, al-Shabaab has referred to an increase in US military air strikes under President Donald Trump, accusing Washington of killing innocent civilians.
According to the Institute for Security Studies, the United States has 34 known military bases in Africa, from where it conducts "drone operations, training, military exercises, direct action and humanitarian activities”.
AFRICOM said in April it had killed more than 800 people in 110 strikes in Somalia since April 2017.
The spate of attacks highlights the group's resilience and capacity to inflict mass casualties at home and in the region, despite losing control of major urban areas in Somalia.
In a November report, a UN panel of experts on Somalia noted an "unprecedented number" of homemade bombs and other attacks across the Kenya-Somalia border in June and July last year.