Islamist group al Shabaab on Monday claimed responsibility for a bomb blast in Mogadishu that killed at least 90 people over the weekend while Somalia said a foreign government that it did not identify helped plan the attack.
The bombing was the deadliest in more than two years in a country wrecked by nearly three decades of Islamist violence and clan warfare.
In an audio message, al Qaeda-allied al Shabaab claimed responsibility for the bombing at the busy Ex-Control checkpoint northwest of Mogadishu.
"The blast targeted a convoy of Turkish and Somali forces and they suffered great loss," Ali Mohamud Rage, al Shabaab's spokesman said in the message.
The National Intelligence and Security Agency did not name the country that it said was involved in the blast. "A foreign country planned the massacre of the Somalis in Mogadishu on 28 Dec 2019," it said in a tweet.
NISA also said it would use assistance from an unnamed foreign intelligence organisation in its investigation.
Rage accused Turkey of "taking all resources of Somalia" and vowed to continue targeting their personnel in the country.
"We shall always fight...the Turkish who work with the apostate government of Turkey. We are not against innocent Turkish muslim citizens," he said.
Two of those killed were Turkish nationals. A small team of Turkish engineers was present at the time of the blast, constructing a road into the city.
In recent years, Somalia has become an arena for military and diplomatic rivalry between Turkey and Qatar on one side and Saudi Arabia and the United Arab Emirates on the other.
Al Shabaab frequently carries out bombings to try to undermine Somalia's central government, which is backed by the United Nations and African Union peacekeeping troops.
The most deadly attack blamed on al Shabaab was in 2017 when a truck bomb exploded next to a fuel tanker in Mogadishu, killing nearly 600.