This article is more than 9 years old

This article is more than 9 years old

Yemeni forces have opened fire on demonstrators in three major cities, killing at least 18 and wounding hundreds in one of the fiercest bouts of violence witnessed in nearly three months of popular unrest aimed at toppling President Ali Abdullah Saleh.

The clashes between a defected faction of Yemen's army and the republican guard, have raised fears that Yemen may be reaching a critical juncture as public fury continues to mount at the president's refusal to step down.

Violence broke out in the capital when a throng of 2,000 protesters tore away from the main sit-in area at Sana'a University and surged en masse towards the cabinet building in downtown Sana'a with shouts of "God is great" and "Allah rid us of this tyrant".

As they neared their destination they were halted by republican guards who, after trying to disperse them with tear gas and water cannons, began firing live rounds at the crowd.

Soldiers positioned on the balconies and roofs of nearby houses rained bullets down on the angry mob of protesters, who responded by hurling chunks of broken-off paving slabs.

The standoff, which lasted for around four hours, climaxed when soldiers loyal to a defected general, Major Ali Mohsin, arrived in pickup trucks and began returning fire at Saleh's troops.

It was the first time the two sides have clashed in the capital since Mohsin declared his support for the opposition in late March.

Local press reported that a lieutenant colonel, Yahya Muhammad al-Ansi, belonging to the rebel general's first armoured division, was killed in the clashes.

Women and children were amongst those caught up in the ensuing mayhem. Bushra Al-Surabi, a prominent female activist, apparently suffered from a bullet wound to the leg.

A doctor presiding over a bloodied corpse in the corner of a nearby mosque-turned-field-hospital said he counted nine other bodies and that hundreds of others were suffering from bullet wounds.

In the industrial city of Taiz, another centre of popular resistance, two teenage protesters were shot dead by snipers while trying to scale a government building.

Protesters retaliated by torching a police building and blockading a number of ministerial offices.

In the Red Sea port city of Hudaida, another protester was killed when security forces opened fire on marchers trying to occupy the city mayor's office, witnesses said.

With protests entering their consecutive third month and Saleh backing away from a Gulf-brokered initiative which would see him exchange power for immunity, Yemen's youthful protesters have began tightening the bolts on their embattled president.

In the past days the country has been brought to a standstill by nationwide strikes as well as blockades of roads and ports. A planned march on the presidential palace is expected on Friday.

"Yemen is at a dangerous juncture," says Gregory Johnsen, a Yemen analyst from Princeton University.

"Every attempt at mediation, including a recently flawed approach by the GCC [Gulf Co-operation Council], has failed, as Saleh stalls and equivocates on public pledges, hoping to somehow survive in power."

The shootings suggest that Saleh may have given the army the green light to fire on protesters.

"Yemeni Oil-Free blood is apparently invisible to the International Community," said Ibrahim Mothana, a protest leader at Change square. "When will the west condemn this?"

Analysts fear that failure to address Yemen's swelling unrest, particularly its rising unemployment, may benefit al-Qaida in the Arabian Peninsula– an organisation which is already capitalising on lapsed security and an increasingly stretched army.

"The last time al-Qaeda had this much time and space in which to operate, it put together the 2009 Christmas Day attack, which narrowly missed bringing down an airliner over Detroit," said Johnsen.