Deadly clashes erupted between government troops and rebels in suburbs of the Syrian capital and villages in the country's south Friday in fresh violence that killed at least 20 people, including nine soldiers, activists said.

President Bashar Assad is trying to crush the 11-month-old uprising against his rule with a sweeping crackdown. Human Rights Watch said in a new report released Friday that in its bid to snuff out the revolt, the regime has detained and tortured children as young as 13.

With the violence in Syria growing increasingly chaotic, diplomatic efforts at the United Nations to find a solution to the crisis have gained pace. In New York, a senior State Department official said Friday the U.S. is "cautiously optimistic" of strong support for a new UN Security Council resolution condemning the bloodshed in Syria and calling for a political transition in the country.

The official said a draft resolution proposed late Thursday by Morocco would likely clear a Security Council vote later Friday or over the weekend, as it appeared to meet Russian concerns. The official spoke on condition of anonymity due to the sensitive nature of the diplomacy.

"From our perspective, this resolution fully supports the Syrian people and the Arab League," the official said.

Armed resistance provokes response

The Syrian conflict has grown more militarized in recent months as army defectors have joined the uprising against Assad and formed a guerrilla force. The armed resistance has in turn provoked a heavier regime assault on areas where defectors are based.

Earlier this week, Syrian troops backed by tanks retook a belt of suburbs on Damascus' eastern outskirts in fierce fighting with rebel soldiers.

Anti-government troops battle regime soldiers on Jan. 31 in Homs province. (Associated Press)

On Friday, similar clashes in the northwestern suburb of Daraya and in the mountains overlooking Damascus left seven civilians dead, activists said. In the towns of Jassem, Kfarshams and Nawa in the southern province of Daraa, clashes killed at least nine soldiers and wounded several others, according to the British-based Syrian Observatory for Human Rights.

In the northern province of Idlib, a roadside bomb killed two boys, state media and activists said. Two others were killed by security forces, according to the Observatory.

The Local Coordination Committees activist group said 21 people were killed nationwide Friday.

Regime allegedly tortures children

The United Nations estimated in January that at least 5,400 people have been killed in the crackdown, including soldiers who defected and those who refused orders to fire on civilians. But the UN has been unable to update its tally because the chaos in the country has made it difficult to cross-check the latest figures.

On Friday, Human Rights Watch said in a new report that it has documented at least 12 cases of children detained under "inhumane" conditions and tortured, as well as children shot in their homes or on the street.

"Children have not been spared the horror of Syria's crackdown," said Lois Whitman, children's rights director for the New York-based group. "Syrian security forces have killed, arrested, and tortured children in their homes, their schools, or on the streets. In many cases, security forces have targeted children just as they have targeted adults."

Also Friday, activists reported protests across Syria, including in the central provinces of Hama and Homs, the northern region of Idlib, in towns and villages in the south as well as areas around Damascus.

The latest protests and clashes came a day after diplomats failed to reach agreement on a UN resolution aimed at ending the bloodshed in Syria, leaving discussions in limbo pending consultations with their home governments.

Envoys said that yet another text is being drawn up for them to send to their capitals for consideration.