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 the southern port of Aden used tear gas and fired bullets in the air to disperse hundreds of protesters, and government supporters wielding clubs attacked demonstrators in the capital Sanaa.

Amnesty International said two people were killed in Sanaa, the first fatalities in the capital since unrest began about two weeks ago.

"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," said Philip Luther, Amnesty International's deputy director for the Middle East and North Africa. "If the authorities continue in this manner, more demonstrators will inevitably be killed."

Yemen, an impoverished country with a weak central government and an active branch of al-Qaida, has been swept up in the protests inspired by successful uprising in Egypt and Tunisia. The demonstrators are demanding that U.S.-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," Saleh said a statement issued by Yemen's Embassy in Washington.

Earlier Wednesday, thousands streamed into a square in Sanaa to bolster anti-government protesters after club-wielding backers of Saleh tried to drive them out.

In the Red Sea port of Hodeida, Saleh supporters attacked a group of anti-government protesters injuring at least 10, according to activists who were taking part in the demonstration.

Security forces in the southern port of Aden used tear gas and fired bullets in the air to disperse hundreds of protesters, officials said.

Seven legislators who belong to Saleh's ruling Congress Party resigned from the group because of the situation in the country and said they will form their own independent bloc, member of parliament Abdul-Aziz Jabbari said. The resignations raise to nine the number of legislators who left the party since protests began.

Also Wednesday, Interior Minister Gen. Mouthar al-Masri met with the U.S. Ambassador Gerald Feierstein and a British envoy, who both expressed concerns about "unjustified violence" against protesters, security officials said.

The ministry said in a statement that al-Masri told the diplomats security forces were neutral and protecting pro- and anti-government gatherings.

In recent days, activists have been digging in, setting up encampments in some areas.

In Sanaa, 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 Wednesday, including academics, writers, artists and scholars.

Thousands of protesters, many of them students, marched through the streets of the port 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 Wednesday, medics said. His death brought to 13 the number of demonstrators killed since the crisis began nearly a month ago.