AL QAA, Lebanon — The United Nations secretary general, Ban Ki- moon, “strongly” urged President Bashar al-Assad of Syria on Wednesday to immediately put into effect a peace plan he is said to have accepted that would rein in security forces in advance of negotiations to end a year of bloody revolt, but activist groups reported more assaults throughout the country.

“There is no time to waste,” Mr. Ban said, speaking in Kuwait

“I strongly urge President Assad to put these commitments into immediate effect,” he said, according to Reuters. “This is an important initial step that could bring an end to the violence and the bloodshed and provide aid to those people who are suffering.”

On Wednesday, activist groups quoted in news reports said government forces continued their drive against Mr. Assad’s adversaries, using heavy weapons to encircle and choke opposition strongholds in several areas

The London-based Syrian Observatory for Human Rights spoke of clashes from the Dera’a region in the south to the area surrounding Hama much further north. The Local Coordination Committees activist group said government troops had stormed the northern town of Saraqeb, leaving 40 people dead and the streets littered with unidentified corpses and wounded citizens after four days of attacks.

The group appealed to the Red Cross and other humanitarian organizations to "treat the injured and bury the martyrs." The group accused government troops of burning and shelling 300 homes and chasing away families related to the government’s opponents. Such reports cannot be verified because the authorities severely restrict access to reporters in an effort to control the flow of information, reducing it often to a trickle.

The United Nations’s top human rights official, Navi Pillay, accused the Syrian authorities of targeting the young.

“They’ve gone for the children — for whatever purposes — in large numbers,” Ms. Pillay said, in an interview with the BBC published on Wednesday. “Hundreds detained and tortured — it’s just horrendous. “Children shot in the knees, held together with adults in really inhumane conditions, denied medical treatment for their injuries, either held as hostages or as sources of information.”

The United Nations raised its estimated tally of the dead in the conflict to more than 9,000, from 8,000 a few weeks ago.

On Tuesday, Kofi Annan, the United Nations special envoy for Syria, reported that Mr. Assad’s government had formally accepted a six- point peace plan. But anti-Assad groups inside Syria reported that at least 57 people were killed throughout the country, including the area bordering this northern Lebanon village. Such fighting suggests that the conflict could be in danger of spilling over into Lebanon. The Lebanese military said Tuesday that no Syrian troops or vehicles had trespassed, although an officer said a mortar shell had landed 40 yards inside Lebanon.

The peace plan has emerged as a focus of diplomacy as the myriad players in the Syria crisis — ranging from external powers to exiled dissidents — sought to increase pressure on Mr. Assad, with varying degrees of unity.

Some of his fractious opponents outside the country, meeting in Istanbul to seek a common front, said late Tuesday they had agreed to reunite under the Syrian National Council, whose Paris-based leadership projects itself as the main umbrella group for exiled dissidents.

But the agreement left out representatives of Syria’s large Kurdish minority, who complained that their demands for special status in a post-Assad era were not being taken into account. News reports said the trade-off for even limited unity had been an agreement by the council’s leader, Burhan Ghalioun, to discuss restructuring the movement in further talks among the exiles in Istanbul on Wednesday.

The Syrian groups were meeting ahead of a gathering on Sunday in Istanbul of the so-called Friends of Syria including many Arab and Western governments seeking Mr. Assad’s ouster.

While Mr. Annan was announcing that Mr. Assad had agreed to his six- point proposal, Mr. Assad’s own representative was visiting with President Mahmoud Ahmadinejad of Iran, one of his few remaining defenders, who called the Syrian conflict a plot by the United States and its allies, including Israel and members of the Arab League, to colonize Syria.

“Today it has become clear to all that the arrogant powers try to harm Iran, Syria and the resistance movement, trying to save the Zionist regime under the slogan of human rights and caring for freedom,” Mr. Ahmadinejad told Faisal Maqdad, a special envoy of Mr. Assad, according to Iran’s state-run news media.

Iran’s official Islamic Republic News Agency made no mention of the Syrian president’s acceptance of the peace proposal by Mr. Annan, appointed as a special representative of both the United Nations and the Arab League. The United Nations Security Council unanimously endorsed Mr. Annan’s effort last week, putting new pressure on the Syrian president.

IRNA said on Wednesday that Mr. Annan himself would visit Tehran next week to discuss the Syrian crisis with Iranian officials. President Ahmadinejad also spoke about the crisis with another visitor, Turkey’s prime minister, Recep Tayyip Erdogan, who has projected himself as a key regional player.

Mr. Assad, who has restricted foreign news coverage of the conflict and has seldom emerged publicly, paid a surprise visit to Homs on Tuesday in which he sought to project an image of responsibility and reason. His army has been locked in an on-again, off-again battle in Homs with elements of the insurgent Free Syrian Army and other antigovernment groups for weeks. The government proclaimed the city safe in early March but last week resumed artillery and mortar barrages of recalcitrant neighborhoods.

Footage broadcast by Syrian state television showed Mr. Assad leading an entourage through the heavily damaged Baba Amr neighborhood, ordering expedited repairs and greeting clots of well-wishers. It was the first time he had visited the city since it was damaged in the fighting.

A voice is heard yelling: “We are with you till death!” Mr. Assad later tells a crowd of supporters, “We will all work together to rebuild Baba Amr, and it will be better than it used to be.”

Anti-Assad activists noted that his visit was not broadcast live and appeared to have been heavily edited and orchestrated. One activist, Abu Jaafar, reached by Skype in the Inshaat neighborhood of Homs, said the visit had been preceded by many tanks encircling Baba Amr, flyovers by at least four helicopters and “a lot of gunfire.”

Others said it was odd that Mr. Assad had been greeted by any residents because so many had fled from the shelling. Syrians who had taken refuge over the Lebanese border near Al Qaa said they suspected that Assad supporters had been transported to the event. “They bring people on buses to clap for him and say that he killed all the Free Syrian Army,” said a man living across the border in a Lebanese farmer’s house who identified himself as Abu Munzer.

Anne Barnard reported from Al Qaa, Lebanon, and Alan Cowell from London. Reporting was contributed by Hwaida Saad and Hala Droubi from Beirut, Lebanon; Rick Gladstone from New York; Sebnem Arsu from Istanbul; and Steven Lee Myers from Washington. (Copyright 2012 The New York Times Company 03/29/12)