"The reports now of attacks by regime fighter jets in Aleppo mark yet a further dangerous escalation and underlines that there are no boundaries that the Assad regime will not cross in the misguided hope that it can resist the will of its people and hang on to power," British Ambassador Mark Lyall Grant told the U.N. Security Council on Wednesday.
Thursday's front page of Syria's pro-regime newspaper al Watan carried the headline "Aleppo ... the Mother of all Battles."
For his part, al-Assad sent a congratulatory message Tuesday to Kim Jong Un, the recently installed supreme leader of North Korea, the state-run KCNA news agency reported Thursday.
"I would like to express my deep thanks to Your Excellency, the leadership of the DPRK and the friendly Korean people for having rendered support and encouragement to our just cause against the moves of the world powers to interfere in our internal affairs," it said.
Meanwhile, Herve Ladsous, the under-secretary-general for peacekeeping operations, told reporters Thursday in Damascus that half of the 300 U.N. observers sent to Syria in April have been sent home, but are prepared to return should circumstances change.
"And that is our sincere hope," Ladous told reporters.
The decision was made after "we found ourselves with too many people with not enough to do," he said.
The monitors' mission was suspended in June, when officials deemed it too dangerous for them to continue their work. They remained in Syria prepared to resume their efforts to monitor compliance with a six-point peace plan brokered by U.N. and Arab League joint special envoy to Syria Kofi Annan once the conditions changed.
Ladsous was not optimistic that would happen soon. "Unfortunately, as of today, I cannot say that we see many indications that a decrease in violence will happen overnight. I say again, Syrians killing Syrians is something that should not continue."
As the violence spirals, many civilians have become internally displaced or fled over the border and fears of sectarian conflict have grown.
Asked Thursday if Ankara was considering establishing safe zones in northern Syria to counter any threat to Turkey's security from the Kurdistan Workers' Party, or PKK, Prime Minister Recep Tayyip Erdogan was noncommittal but said officials were discussing their options.
"It is out of question that we would allow a terrorist organization to be based in northern Syria and become a threat to our country," he said in televised remarks.
"All of these are among alternatives -- safe zone, buffer zone or camps such as the ones we have now -- all of these are among alternatives," he said. "Our Foreign Ministry, armed forces, intelligence organizations are working on this, and decisions or steps that will need to be taken will be taken when the time comes."
Turkey and the United States consider the PKK a terrorist group.
Speaking Thursday at a memorial to those who died in the Srebrenica massacre in the Balkans in the 1990s, U.N. Secretary-General Ban Ki-moon urged the Syrian government and the opposition forces to cooperate with the United Nations in ending the conflict.
The U.N observer mission in Syria has been unable to do its job "because of the noncompliance of the parties -- the government parties and also opposition forces," he said.
The six-point peace plan must also be implemented "without further delay," he said.
"At this time again I am urging all the parties: They must stop fighting and killing people now. They have to begin political dialogue for a political resolution of this crisis," Ban said.
After 16 months of chaos, more officials from al-Assad's regime have resigned.
The opposition Syrian National Council said Wednesday that two senior Syrian diplomats were the latest to defect.
One was the Syrian ambassador to the United Arab Emirates, Abdullatif Al Dabbagh, SNC spokesman George Sabra said.
The second is Al Dabbagh's wife, Lamia Al Harriri, who was a Syrian envoy to Cyprus. She defected to Qatar, SNC member Najy Tayyarah said. Al Harriri is also the niece of Syrian Vice President Farouq Al Sharea.
But on Thursday, a Syrian official downplayed the reports of recent defections.
Syrian Foreign Ministry spokesman Jihad Makdissi said Dabbagh "was called to Damascus for consultations with the minister and has been off duty ... since June 4."
In addition, Makdissi said, Al Harriri has never been a Syrian ambassador. "She is a diplomat who was tasked with managing affairs on behalf of the embassy charge d'affaires pending the appointment of an ambassador."