President Ali Abdullah Saleh on Thursday ordered an investigation into the clashes that erupted on Wednesday between police and marchers in Aden.

Confrontations ensued between the angry demonstrators and the police. A government building was burned. The vice president also arrived in Aden in an attempt to contain the escalating situation.

Meanwhile, demonstrations have intensified and spread to other provinces.

In Sanaa, thousands of people gathered in the streets calling for Saleh to step down.

The demonstrators faced off with counter protesters organized by government loyalists. The two gatherings clashed with some wielding batons, daggers or stones.

Demonstrators torched car tires and garbage bins. Journalists were caught in the scuffle; some were injured while others saw their equipment smashed.

The Ministry of Interior said authorities resorted to firing bullets to disengage the demonstrators.   

Observers warn that if the fighting continued in the streets, both sides could use their weapons and turn the capital into a battlefield. Yemen is one of the most heavily armed countries.

Inspired by the demonstrations in the north, southern secessionists organized protests of their own in Aden Lahji, Abyan and Shabwa.

Officials accused the media of adding fuel to the fire and distorting the facts.

An anonymous official source told the state-run Saba Agency that the media lacked the objectivity due to their reliance on false, misleading and biased information aiming at provocation.

"These statements stir up the situation and encourage violence rather than sitting at the dialogue table. Those agendas aim to stir up sedition and hinder democracy from achieving change through the ballot box and incite anarchy, which does not serve Yemen"

In another development in Hadramout, a senior security official was fatally shot on Wednesday evening in the coastal city of Sheher. The official, only identified as Al-Azi, was found dead behind a school. It was not known who carried out the attack.