SANA'A // Yemen's president said he had ordered his security services to protect protesters, stop all clashes and prevent direct confrontation between government supporters and opponents.
Wednesday's directive came at the end of the day when security forces in Aden used tear gas and fired bullets in the air to disperse hundreds of protesters, and government supporters wielding clubs attacked demonstrators in Sana'a.
Amnesty International said two people were killed in Sana'a, the first fatalities in the capital since unrest began about two weeks ago.
Philip Luther, Amnesty International's deputy director for the Middle East and North Africa, said: "This disturbing development indicates that the heavy-handed tactics which we have seen the security forces using with lethal effect against protesters in the south of Yemen are increasingly being employed elsewhere. If the authorities continue in this manner, more demonstrators will inevitably be killed."
Yemen has been swept up in the protests inspired by uprisings in Egypt and Tunisia. The demonstrators are demanding that the US-backed president, Ali Abdullah Saleh, in power for 32 years, step down. But he has said he will step down after national elections in 2013.
"The Government of the Republic of Yemen will continue to protect the rights of its citizens to assemble peacefully and their right to freedom of expression," Mr Saleh said a statement issued by Yemen's Embassy in Washington.
Earlier Wednesday, thousands streamed into a square in Sana'a to bolster anti-government protesters after club-wielding backers of Mr Saleh tried to drive them out.
In recent days, activists have been digging in, setting up encampments in some areas.
In Sana' a, protesters have been camping in a square near Sanaa University. On Tuesday, they came under attack by pro-government forces who witnesses say swung clubs and fired in the air. But the government forces failed to dislodge the protesters, and thousands more streamed into the square in support on Wednesday.
Thousands of protesters, many of them students, marched through the streets of al Mukalla in eastern Yemen, chanting, "The people want the downfall of the regime."
Demonstrators overturned and set fire to a government car and threw stones at the police who fired tear gas and rubber bullets.
A 16-year-old was seriously injured when a tear gas canister struck his face, medical officials at a hospital said.
A 19-year-old wounded in Aden last week died of his injuries on Wednesday, medics said. His death brought to 13 the number of demonstrators killed since the crisis began nearly a month ago.
