By Abdi Sheikh and Feisal Omar
MOGADISHU (Reuters) - A car bomb exploded in the heart of the Somali capital on Wednesday, wounding two people in an attack Somalia's al Shabaab rebel group said was carried out by its militants.
The blast, which triggered bursts of gunfire in Mogadishu, was the latest in a wave of bomb attacks in the country where the embattled U.N.-backed government is struggling to secure the city against al Qaeda-linked Islamist rebels.
"We were behind the car bomb explosion. We targeted security forces," Sheikh Abdiasis Abu Musab, a spokesman for al Shabaab's military operations, told Reuters.
The blast happened in Mogadishu's busy administrative district, near the bustling Kilometer 4 road (K4) junction. Police said four suspects had been detained and that they were investigating a second suspicious vehicle in the city.
There has been a surge in suicide bombings and remotely detonated blasts in Mogadishu since al Shabaab pulled most of its fighters out of the coastal city in August, vowing to turn increasingly to al Qaeda-inspired tactics.
Al Shabaab carried out a truck bombing in October which killed more than 70 people, the group's deadliest attack since the start of their rebellion in 2007. A spate of smaller attacks has followed.
The militants have been weakened in past months, on the back foot against African Union soldiers in Mogadishu and after losing territory to Kenyan and Ethiopian forces in southern and central Somalia. There are also signs of growing internal divisions within the rebel ranks.
Piracy has also flourished in the chaos of the last two decades. On Wednesday, pirates freed British hostage Judith Tebbutt more than six months after shooting dead her husband, after receiving a ransom.
In Mogadishu, witnesses told Reuters the car laden with explosives had been parked on Mogadishu's Maka al Mukarram road which links K4 to the presidential palace, arousing the suspicions of security forces who blocked off traffic.
"We got a man with the remote control seconds after he detonated the car. We also arrested three other suspects," police spokesman Abdullahi Barise said.
A Reuters photographer who saw the wreckage of the car, said one of the victims had been taking photos of the 4x4 vehicle at the time of the explosion.
The man who was bleeding heavily cried out in pain as onlookers helped him. One family had fled their house just meters away moments before the bomb blew up.
Several hours after the first blast, police said they had cordoned off the K4 intersection to investigate another vehicle abandoned in an area used by waiting taxis.
"We didn't recognize the car. All taxi drivers fled the parking. It is a suspected car bomb," witness Jama Hussein told Reuters. Security forces were holding people back from the scene, he said as police awaited the arrival of bomb disposal experts.
(Writing by Richard Lough; Editing by Yara Bayoumy and Maria Golovnina)