(CNN) -- As Syria weathered more bloodshed this week, the Bashar al-Assad regime faced more political pressure and derision from two important corners -- members of the country's fledgling opposition movement and America's top diplomat.

Hundreds of Syrian activists gathering in the Turkish city of Antalya called on al-Assad to step down and hand over power to his vice president with the goal of organizing general elections. They also declared its support for the "Revolution in Syria" and elected a 31-member council aimed at assisting the protest movement.

Secretary of State Hillary Clinton, speaking in Washington, repeated President Barack Obama's recent tough words to al-Assad in his policy -- embrace democracy or get out.

"The legitimacy that is necessary for anyone to expect change to occur under this current government is -- if not gone -- nearly run out," Clinton said.

"The international community has to continue to make its strongest possible case and call for specific action, not just an amnesty, but the release of political prisoners, an end to unjust detentions, let human rights monitors into the country."

Since mid-March, Syria's government has undertaken a fierce crackdown against demonstrations that have demanded reforms of al-Assad.

Human Rights Watch accused Syria on Wednesday of carrying out a "systematic" series of abuses against protesters in Daraa province. In a report detailing abuses toward protesters, it called on the United Nations to investigate.

Since Sunday, at least 43 people have been killed, when government forces entered Homs province to end protests against government rule, said Rami Abdel Rahman, president of the Syrian Observatory for Human Rights.

A witness in Rastan, who identified himself as a protest organizer named Abu Abdullah, said there was heavy artillery fire and that shelling had destroyed about 20 homes and several mosques.

Abdullah said the fighting has been nonstop since troops cut off the town on Sunday. He said he carried the body of a 16-year-old boy killed in the attack on the city.

"He was just walking in the street when he was shot," he said.

CNN has not been granted access into Syria and is unable to independently verify the accounts.

Syria has denied the allegations, but there is growing international criticism of the regime, and opposition members are trying to mount a stronger movement.

Security forces have killed more than 887 across the country since the protests started in mid-March, Human Rights Watch said in a report.

That number does not include security personnel the government claims died in attacks from "armed groups."

Precise "numbers are impossible to verify given the information blockade imposed by the Syrian government," the rights group said.

The Syrian crisis was center stage in Antalya on Thursday, where hundreds of activists from Syria and the international diaspora gathered at a hotel to discuss ways to support the uprising.

Dozens of regime supporters picketed the gathering, and Turkish police were out in force in Antalya, ensuring that the pro-government demonstrators could not reach the opposition conference venue.

Conference organizers say their main goals are to organize committees aimed at supporting protesters inside Syria, communicating with the media, and lobbying foreign governments. Their aim, they say, is to help unite the opposition both inside and outside Syria.

In Washington, the rhetoric toward Bashar al-Assad's regime heated up as it has around the world. On Wednesday, for example, Australia's foreign minister said Syria's actions should be referred to the International Criminal Court.

The United States has taken steps, including sanctions and executive orders, to put pressure on the regime, Secretary of State Clinton said. While the United States is trying to deal with the issue, Syria hasn't spurred the same kind of international unity that the Libyan crisis has, she said.

"Right now the attitude of the international community is not as united as we are seeking to make it. We do not yet have the agreement by some of the other members of the Security Council. We certainly have nothing resembling the kind of strong action the Arab League took with respect to Libya.

"So every day that goes by, not only do we see the outside pressure growing in a public effort to try to end the violence and bring this terrible chapter to an end, but privately we continue to do everything we can with like-minded countries," she said.

The killing of a Syrian teen during the recent military siege in the southern province of Daraa has enraged people across the world, including Clinton.

"The tragedy of the young boy, Hamza Ali al-Khateeb, symbolizes for many people around the world the total collapse of any effort by the Assad government to work with their own people," Clinton said.

She said al-Assad hasn't called for an end of violence and isn't "engaged seriously" in reform.

"When we find ourselves in these situations we have to do a very clear-eyed, calculated assessment of what influence we have, and who are our partners in trying to bring about that influence. Although there are general trends in the Middle East and North Africa, each country is a specific case onto itself," Clinton said.

U.S. Rep. Keith Ellison, a Democrat from Minnesota who is a Muslim, said on Thursday "the world will not forget" the regime's actions and called on people to stand against the regime's human rights violations.

The majority of people in Syria are Sunni Muslims but the regime is dominated by Alawites, whose faith is a spin-off of Shiite Islam.

CNN's Elise Labott, Ivan Watson and Salma Abdelaziz contributed to this report