ADEN: Clashes between Yemeni troops and secessionist militants killed four people Friday in southern Yemen, two of them soldiers, sources on both sides said.

The fighting broke out when the militants ambushed a military vehicle, killing the soldiers and wounding four others, a military source told AFP.

Two militants died in the fighting in the town of Daleh, said Abderrahim al-Naqib, from the Southern Movement, accusing the army of bombing residential areas and a hospital.

Naqib said a third militant was "clinically dead" and 21 fighters wounded.

Tensions have soared in southern Yemen following deadly clashes at the end of December in which secessionists stormed a governor's office to raise the flag of the former South Yemen.

Two policemen and a civilian died in that fighting. The following day, 19 people were killed when the army shelled a funeral tent, according to militants and medical sources.

After British colonial rule ended in 1967, southern Yemen was independent until union with the north in 1990.

A secession attempt four years later sparked a brief civil war that ended with northern forces taking over the south.

Southern grievances have hindered the political transition following the 33-year rule of Ali Abdullah Saleh, who stepped down last year following Arab Spring-inspired protests.