"How many more people will be killed if the current situation continues?," Ban said, speaking at a conference of donors in Kuwait called to drum up more pledges of financing for UN humanitarian efforts.
"I appeal to all sides and particularly the Syrian government, to stop the killing ... in the name of humanity, stop the killing, stop the violence," he said.
More than 60,000 people have been killed since the 22-month-old conflict began, the United Nations says.
The world body warned on Monday that without more money it would not be able to help millions of Syrians and appealed for donations at the aid conference to meet its $1.5 billion target.
Some four million Syrians inside the country need food, shelter and other aid and more than 700,000 more have escaped to neighboring countries since the conflict began, according to the United Nations. Half of the civilians affected by the crisis are children, it says.Scale of crisis escalates
Wednesday's conference will seek pledges of $1 billion of aid for Syria's neighbors sheltering refugees and another $500 million to bankroll humanitarian work for 4 million Syrians inside the country.
The aid would fund operations for the first half of this year, but the United Nations has so far received pledges covering just 18 percent of the target, unveiled last month as the scale of Syria's humanitarian crisis escalated sharply.
Even if pledges are made, aid groups have found in the past that converting promises into hard cash can take time.
Nevertheless, there was early positive news for the gathering when Kuwait's emir pledged to give $300 million to the aid effort.
Sheikh Sabah al-Ahmad al-Sabah told the meeting that "horrifying reports" of violence had raised questions over the future of Syria and aid efforts had to be redoubled.
But Ban said much more remained to be done.
"The situation in Syria is catastrophic and getting worse every day," he said. "Every day Syrians face unrelenting horrors," he said, adding this included sexual violence and detentions.Infrastructure being destroyed
About half of public hospitals and a quarter of schools are damaged, he said, and the country's infrastructure was being systematically destroyed.
Aid officials hope the fact that the conference is being held in Kuwait will encourage other wealthy Gulf Arab states, who have led regional opposition to President Bashar Assad, to support the international aid effort.
Many Gulf states have sent assistance, but aid workers say their efforts have been haphazard and rarely coordinated with other aid agencies, hampering their ability to plan a sustained relief program.
Syria's main opposition coalition has criticized the UN appeal and its arrangements for distributing aid inside Syria, saying the organization has effectively ceded control to the Syrian government and failed to deliver all but a bare minimum of aid to areas controlled by Assad's opponents.
DUBAI (Reuters) -- Denouncing "unrelenting horrors" in Syria's war, UN Secretary-General Ban Ki-moon appealed on Wednesday for an end to the violence and urged more aid to address a situation he said was catastrophic and worsening by the day.