|Protesters are seeking to oust president Ali Abdullah Saleh, a key US ally in the fight against al-Qaeda [Al Jazeera]
A teenager was killed and four people were wounded in a clash with soldiers in Yemen's southern port of Aden, witnesses said.
They said soldiers opened fire at the youths who were throwing stones at their military patrol in the city's Khormaksar district on Monday.
The death brings to 12 the number of people killed in unrest in Yemen since Thursday. Protesters, seemingly inspired by uprisings in Egypt and Tunisia, have called for the end of president Ali Abdullah Saleh's rule.
Saleh, in power since 1978, said on Monday that only defeat at the ballot box will make him quit.
"If they want me to quit, I will only leave through the ballot box," Saleh told a news conference as thousands of protesters, including opposition MPs, gathered outside Sanaa University to demand his departure.
|Protests have continued despite Saleh promising not to seek re-election when his term ends in 2013 [Reuters]
"We have offered a package of reforms in a meeting with the parliament," Saleh said, adding: "It was in response to calls by the opposition, but unfortunately, as soon as we made it and were endorsed by the people the opposition raised the bar of its demands. And whenever we would offer more concessions, they would ask for more."
The EU delegation to Yemen issued a statement strongly condemning the use of violence against peaceful protesters and urging Saleh to respond to "the legitimate aspirations of the Yemeni people".
"The EU calls for the Yemeni authorities to immediately halt attacks by security forces and armed pro-government groups on peaceful protesters and journalists and avoid any escalation.
"The EU deeply deplores the loss of lives and calls on all to exercise restraint and calm in order to avoid further casualties and violence," the statement read.
Saleh, a US ally battling a resurgent al-Qaeda wing based in Yemen, faces soaring unemployment, dwindling oil and water reserves, and chronic unrest in northern and southern provinces.
Shots were also fired at the demonstration in Sanaa, as the anti-government protests entered their 11th consecutive day. Thousands of people also staged sit-ins in the cities of Ibb and Taiz on Sunday.
Amid the ongoing turmoil, authorities have detained a leader of the separatist Southern Movement in Aden.
Hasan Baoum was arrested in the southern port city by an "armed military group" in a hospital where he was receiving treatment and was taken to an unknown location, his youngest son Fadi Hasan Baoum told the Reuters news agency.
Baoum was also arrested in November last year, accused of planning illegal demonstrations.
Yemeni clerics issued a statement on Monday prohibiting the use of force against protesters, which they described as a "crime," and calling for a ban on arbitary arrest and torture.
Security in Aden had been stepped up on Sunday with tanks and armoured vehicles out on the city's main streets.
In the capital, as many as 50 government supporters tried to break up a demonstration outside Sanaa University by more than 3,000 protesters.
Marching students chanted and carried signs reading: "Get out Ali for the sake of future generations".
A Saleh supporter fired shots from an assault rifle but there were no reported casualties and the government supporters soon dispersed, while the protesters continued their demonstration chanting, "Leave, Ali!"
Both sides fired weapons on Saturday outside the university - the first reported use of firearms by demonstrators.
Five soldiers were wounded on Saturday evening in Khormaksar and Sheikh Othman when protesters clashed with security forces, a local official and witnesses said on Sunday.
In the southern city of Ibb, around 1,000 protesters set up camp in Freedom Square waving banners which read "Leave" and "The people want the fall of the regime", witnesses said.
In Taiz, thousands continued a sit-in for the 11th straight day. Twelve Yemeni human rights organisations demanded the sacking and trials of security officials in Aden, Sanaa and Taiz because of their role in attacks against demonstrators, according to a statement seen by Reuters.
Saleh on Sunday renewed his call for opposition parties to continue their dialogue and blamed the previous two days of protests, in which five people were killed, on "elements outside the system and the law".
"Dialogue is the best way. Not sabotage. Not blocking the roads," he told tribal, military and civil leaders in Sanaa.
Al Jazeera's Hashem Ahelbarra, reporting from Sanaa, said Saleh's message to the pro-democracy protesters is clear: "There is no way he can allow them to bring about change by taking to the streets".
"The government has also been saying, over the last few days, that calls for independence in the South won't be tolerated."