President Ali Abdullah Saleh's return comes amid a surge of violence in the capital Sanaa, rocked by clashes between loyalist troops and forces backing a mass protest movement calling for his overthrow.

Within minutes of the announcement, loud bursts of gunfire and explosions were heard echoing through the capital.

A Reuters witness said the road to Sanaa's military airport was blocked on Friday morning.

Saleh has clung to his 33-year rule despite pressure to sign a power transition deal and a bomb attack on his compound in June that left him severely wounded.

Protesters took to the streets in January, inspired by uprisings across the Arab world.