Aden (Yemen): Police killed four people and injured 40 on Saturday as the biggest protests swept impoverished Yemen, demanding President Ali Abdullah Saleh to step down after three decades in power.

Security forces here used live ammunition on a demonstration, inspired by revolts that toppled the presidents of Tunisia and Egypt.

The deceased were identified as 17-year-old Mohammed Ahmed Saleh, 21-year-old Hael Walid and Salem Bashaj. A hospital official in Aden confirmed that the fourth protester had died of wounds sustained in the gunfire.

President Saleh has refused to resign and said he will not seek re-election. Anti-regime protests since February 16, have taken the death toll to 19 and wounding several others.

Residents of the Aden district of Maalla, where the raid happened, have begun to fear their city has become the frontline in a state-sponsored war.

Clashes between police and protesters on Friday continued through the night. Witnesses said security forces opened fire at a sit-in outside a hotel on the main street in Maalla to demand the departure of Saleh.

In the capital Sanaa, tens of thousands of protesters poured into a main square near Sanaa University chanting "Out, out!" and "God bears witness to your acts, Abdullah," according to a report.