Turkey bluntly told Syrian President Bashar al-Assad to step down for the sake of his people, tightening regional pressure on Damascus while the wider world condemned Syria's violent crackdown on protests in a vote at the United Nations.

Activists said Syrian forces killed 21 civilians and five army deserters on Tuesday. Among those killed were four children shot dead by troops near a school in the central region of Houla and a 12-year-old killed at a protest in the eastern city of Deir al-Zor, the Syrian Observatory for Human Rights said.

It was not possible to independently confirm the killings as Syrian authorities, who blame the unrest on armed terrorist groups, have barred most independent media from the country.

The United Nations says 3,500 people have been killed since the protests erupted in March, triggered by Arab uprisings which toppled the leaders of Tunisia, Egypt and Libya.

Without spilling any more blood, without causing any more injustice, for the sake of peace for the people, the country and the region, finally step down, Turkish Prime Minister Tayyip Erdogan said on Tuesday, in his first direct call for Assad to go.

In a further sign that Turkey was stepping up pressure on Syria, Turkish media reported that Turkeys' land commander inspected troops near the border.

Bashar al-Assad comes out and says 'I will fight to the death'. For the love of God, who are you fighting with? asked Erdogan. Fighting your own people until the death is not heroism. It's cowardice. If you want to see someone who fights his people to the death, look at Nazi Germany, look at Hitler, look at Mussolini, he told his ruling AK party.

If you cannot learn a lesson from them, look at the killed Libyan leader who turned his guns on his own people and only 32 days ago used the same expressions as you.

But, echoing the stance of Arab League foreign ministers who suspended Damascus and have threatened economic and political sanctions, he said his criticism did not mean Turkey was calling for international military action.

We do not have eyes on any country's land, we have no desire to interfere in any country's internal affairs, Erdogan said.

SYSTEMATIC VIOLATIONS

Highlighting Syria's growing isolation, 122 countries voted for a resolution at the U.N. General Assembly's human rights committee condemning the government crackdown. Only 13 countries voted against and 41 abstained.

The resolution says the committee strongly condemns the continued grave and systematic human rights violations by the Syrian authorities, such as arbitrary executions, excessive use of force and the persecution and killing of protesters and human rights defenders.

It also demands an immediate end to arbitrary detention, enforced disappearances, torture and ill treatment of detainees, including children in Syria.

Russia and China, which vetoed a European-drafted U.N. Security Council resolution last month that would have condemned Syria and threatened possible future sanctions, abstained according to an official U.N. tally, which diplomats said could indicate a shift in their positions.

Countries that voted against the resolution included Iran, North Korea, Belarus, Nicaragua, Venezuela and Vietnam. Syria's U.N. Ambassador Bashar Ja'afari said the resolution, drafted by Britain, France and Germany, had no meaning for Damascus.

Although the draft resolution is submitted primarily from three European countries it is not a secret that the United States of America is the mastermind and main instigator of the political campaign against my country, Ja'afari said.

This draft resolution definitely has nothing to do with human rights; it is only a part of the typically hostile policy by the United States against Syria, he said.

Ja'afari held up for delegates what he said were documents naming terrorists arrested while smuggling arms into Syria. He said the documents offered clear proof of a U.S.-led plot to topple Assad.

German Ambassador Peter Wittig said it was time to move the issue back to the 15-nation Security Council, which has been deadlocked on Syria due to Russian and Chinese opposition.

The Security Council cannot fall behind the region, he said, referring to the Arab League suspension of Syria. We would encourage the ... council to come back to this issue.

British Foreign Secretary William Hague said in a statement that the resolution sends a signal of united condemnation of the Syrian regime's systematic human rights abuses.

As long as the crisis in Syria continues the international pressure on the Assad regime will only intensify, he said.

U.S. Ambassador Susan Rice also welcomed the committee's adoption of the resolution, which will be confirmed by a new vote in a plenary meeting of the General Assembly next month.

By overwhelmingly adopting its first-ever resolution on Syria's human rights abuses, the ... Third Committee has sent a clear message that it does not accept abuse and death as a legitimate path to retaining power, she said in a statement.

(Additional reporting by Khaled Yacoub Oweis in Amman and Louis Charbonneau at the United Nations; Writing by Dominic Evans; Editing by Jon Hemming)