As Turkish military vehicles roll toward the Syrian border and an explosion rocked a landmark building in downtown Damascus, a defiant Bashar al-Assad blamed his neighbour for the rising violence.
In an interview broadcast on Thursday, the Syrian President did not apologize for recently shooting down a Turkish fighter jet and he made little effort to back out of the growing confrontation with his former allies in Ankara, whom he accuses of helping rebels.
"The policies of the Turkish officials lead to the killing and bloodshed of the Syrian people," Mr. al-Assad said.
The bloodshed escalated when two magnetic bombs exploded in judges' cars near a court building on Thursday, the third strike this week against symbols of regime power in the capital.
Rebel ambushes and bombings in Damascus "substantially increased" this spring, according to the U.S. Institute for the Study of War. Researchers counted 10 bombings within the capital during May, up from zero in February, part of sixfold rise in rebel attacks in the city since winter.
Such a dramatic increase in rebel activity within Damascus, dominated until now by security forces, suggests the armed revolution may be gaining strength.
Peace negotiations remain weak, meanwhile; diplomats preparing for another round of talks on Saturday have already failed to agree about what happened during their previous session.
U.S. Secretary of State Hillary Clinton told reporters on Thursday that it was "very clear" that all participants in a recent gathering – including Russian envoys – had approved a plan for transition of power.
Earlier in the day, however, Russian Foreign Minister Sergei Lavrov denied any softening in Moscow's position, saying no resolution had been reached, and complaining bitterly that "working formulas" had been leaked to the press in what he called "an unfair approach to diplomacy."
Mr. Lavrov and Ms. Clinton planned to meet in St. Petersburg to work out their differences ahead of discussions with a broader group of countries in Geneva this weekend. The meeting will include all permanent members of the UN Security Council – China, France, Russia, the United Kingdom and the United States – along with representatives of Turkey, the European Union, the Arab League, Kuwait, Qatar and Iraq.
UN envoy Kofi Annan wanted Iran to attend because of Tehran's key role in supporting the Assad regime, but the proposal faced objections from the United States and Britain and it appears that Iran will be excluded from the talks.
Diplomats expressed optimism this week that they may reach an agreement about a so-called "national unity cabinet" with representatives from both Mr. al-Assad's regime and the opposition.
Developments on the ground continue to shift the conflict away from a settlement, however. A Turkish state news agency said armoured military vehicles were being transported to two military installations near the border, and news footage showed mobile surface-to-air defence units transported along the main avenues of Turkish towns.
Israel appeared to be taking similar precautions; an Israeli military official gave a tour for reporters along the border on Thursday and described upgrades to defence infrastructure to prevent cross-border attacks.
The Syrian Observatory for Human Rights counted at least 69 people killed on Thursday, including 38 civilians. The activist group, whose statistics were cited in a UN report this week, said that June now ranks as the deadliest month of the 16-month conflict.
UN observers have noted that the killing remains largely one-sided, with regime forces pounding civilian neighbourhoods with artillery and other heavy weapons, but some deaths have been difficult to attribute amid the chaos.
The Palestinian group Hamas said on Thursday that one of its members, Kamal Husni Ghanaja, had been killed in his home in Damascus. Reuters reported that the mid-level Hamas member appeared to have been tortured before his death.
No group immediately claimed responsibility for the killing, but some observers noted that Mr. Ghanaja's former boss, Mahmoud Mabhouh, was killed in an apparent hit by the Israeli spy agency Mossad at a five-star Dubai hotel in 2010.
The UN issued an appeal for emergency funding on Thursday to handle the flood of refugees now spilling out of Syria. A UN statement said that, on average, humanitarian agencies have registered 500 refugees a day for the past three months.