International envoy Kofi Annan says world powers share a "profound concern" that Syria's violence is spiraling into civil war but have pledged to deploy 300 truce monitors there by the end of the month.

Annan said Tuesday in Geneva that there has been "a spate of bombings that are really worrying" and that the U.N.'s cease-fire-monitoring mission "is the only remaining chance to stabilize the country."

He told reporters after briefing the U.N. Security Council by videoconference from Geneva that "there is a profound concern that the country could otherwise descend into full civil war, and the implications of that are frightening."

Annan said failure to prevent a civil war "will not only affect Syria, it will have an impact on the whole region."

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

GENEVA (AP) _ International envoy Kofi Annan told the U.N. Security Council on Tuesday that "unacceptable levels of violence and abuse" are continuing in Syria and warned that the country could plunge into civil war if his peace mission doesn't succeed, council diplomats said.

Two diplomats, speaking on condition of anonymity because Annan's videoconference briefing from Geneva was closed, said the U.N.-Arab League envoy reported fewer large-scale military operations and that the presence of U.N. military observers and interventions in several instances appear to have had a calming effect.

But the diplomats said Annan stressed that much more remains to be done, saying government troops are still present in and around cities and towns, human rights violations are extensive and may be increasing, humanitarian assistance is insufficient and the government is denying "the legitimate aspirations of the Syrian people."

Annan told the council the onus remains on the government to create a climate where all Syrians will reject further militarization of the conflict, the diplomats said. While the government has taken steps, Annan was quoted as saying it "has clearly not responded to the needs of the people."

He warned that his six-point peace plan aimed at halting the fighting and initiating political talks to end the 13-month conflict is not open-ended, and stressed that the mission is "the only remaining chance to stabilize the country," the diplomats said.

The U.N. Security Council has endorsed Annan's plan and authorized 300 unarmed military observers to monitor actions by the government and opposition for three months.

The International Committee of the Red Cross earlier said the conflict is transforming into a guerrilla war, with combatants carrying out ambushes and bombings instead of sustained battles, and it warned that more than 1.5 million Syrians are struggling to meet basic needs like food, water and shelter.

Fighting in the central city of Homs, where U.N. observers helped halt weeks of artillery attacks, and in the northern Syrian town of Idlib are now non-international armed conflicts, said Jakob Kellenberger, president of International Committee of the Red Cross.

The distinction that this is an internal armed conflict is important because under international humanitarian law the government and opposition gain additional rights to use force but could be held accountable for possible war crimes.

Annan told the Security Council that one million Syrians are in need of humanitarian assistance and he strongly urged the government "to accept conditions for the scaling up of humanitarian assistance without delay," a council diplomat said.

Tens of thousands of people are living in public buildings or other people's homes, and the Red Cross and Syrian Arab Red Crescent is feeding about 100,000 "particularly vulnerable" Syrians, Kellenberger said.

Kellenberger also said ICRC has gained permission to visit detainees at Aleppo's central prison from May 14-23 and is pushing for access to others. One diplomat quoted Annan as saying about prisoners, "I had expected much faster progress and much higher numbers of releases."

What began as a largely peaceful protest movement has evolved into more Syrians taking up arms in the face of President Bashar Assad's violent crackdown on dissent. The U.N. says more than 9,000 people have been killed in the past 14 months since Assad, who inherited power from his father in 2000, began his crackdown.

The Red Cross, meantime, said it is appealing for $27 million to quickly scale up aid.

About 40 U.N. observers have been trying to restore calm, but so far the intervention by world powers has failed to deter the bloodshed. A larger force of 300 U.N. observers is being prepared to enforce the truce.

Officials are also concerned about Syrians flocking over the borders.

International Organization for Migration spokesman Chris Lom said Tuesday that 2,835 Syrians have registered at the Domiz refugee camp in northern Iraq since it opened this month and local authorities are expecting up to 7,000 more refugees at Domiz in the next month.

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Frank Jordans in Berlin contributed to this report.