At least four people were killed and 10 others wounded when a car rammed into a busy restaurant and exploded in the Somali capital Mogadishu, local sources told Al Jazeera.

The blast on Tuesday targeted the Bonoodo restaurant located near the city's Central Hotel, which was the scene of a deadly attack in February.

There was no immediate claim of responsibility for Tuesday's attack, but Abdirizak Omar, Somalia's interior minister, wrote on his official Twitter account that seven al-Shabab fighters were killed by the government forces at the site. 

Al-Shabab, which is allied to al-Qaeda, appears to be stepping up attacks in Somalia and across borders.

At least seven people were killed on Monday when an al-Shabab bomb exploded in a UN van in the northern region of Puntland. Four UN staff, working to help Somali children, were among those killed in that attack, the UN children's agency announced on Tuesday.

The group has also attacked neighbouring Kenya last month, which has sent troops to Somalia to fight the rebels. At least 148 people, mostly students, died in the attack on Kenya's Garissa University College.

The United States blacklisted two top leaders of al-Shabab on Tuesday.

Ahmed Diriye, who took over as the group's leader in September 2014, and intelligence chief Mahad Karate, were both designated as "terrorists" by the State Department.

Source: Al Jazeera