Two large blasts, around ten minutes apart, have struck the intelligence headquarters and a police base in Yemen's southern port city of Aden.

A local security official said Thursday's blasts were likely caused by explosive devices that did not manage to penetrate the perimeter walls of the two buildings, which stand around 400 metres apart.

He said a boy had been killed and that several people were wounded when security forces briefly opened fire after the blasts.

No one was injured in the explosions, the official said.

At night, loud explosions and gunfire were also heard in the capital, Sanaa, in the neighbourhood where the chief of the main tribe opposing Yemen's president lives. There were no immediate reports of casualties.

Mohammad al-Qadhi, former managing editor of Yemen Times, told Al Jazeera that clashes had taken place between fighters supporting Sadiq al-Ahmar, the leader of the most powerful tribal federation, and troops loyal to President Ali Abdullah Saleh.

Saleh, Yemen's leader of nearly 33 years, has held onto power in the face of massive protests demanding his ouster since February. He is currently recuperating in Saudi Arabia after a June attack on his compound.