Two huge bomb blasts killed at least 27 people in Syria's capital on Saturday, sparking anger at Riyadh and Doha, as special envoy Kofi Annan warned of regional fallout from the year-long bloodshed.
An Arab diplomat told AFP Saudi Arabia has started delivering arms to Syrian rebels through Jordan, which was denied by Amman, while rival Iran is already suspected of sending weapons to its Syrian regime allies.
State television said the early morning "terrorist" attacks, apparently car bombings timed minutes apart, had targeted police headquarters in the Duwar al-Jamarek area and air force intelligence offices in Al-Qasaa district.
The explosions killed 27 people, mainly civilians, and wounded 140 civilians and security personnel, the interior ministry said.
As angry residents vented their fury at Arab supporters of anti-regime activists, the state broadcaster ran footage of a charred body inside the mangled remains of a smouldering vehicle in Duwar al-Jamarek.
From Paris, French Foreign Minister Alain Juppe said: "France condemns all acts of terrorism, which cannot be justified under any circumstances."
France has been at the forefront of calls for Assad to quit.
Egypt's Foreign Minister Mohammed Kamel Amr affirmed Cairo's "fixed position against terrorism in any form, regardless of the reasons behind it."
Bombings have hit Syria's major cities in recent months, provoking mounting concern that Al-Qaeda has taken advantage of the uprising against President Bashar al-Assad.
Syria's opposition, however, has accused the regime of stage-managing the attacks.
Commentators on state television blamed Qatar and Saudi Arabia, Assad's fiercest Arab critics over his regime's deadly crackdown on dissent since March 2011. Both countries have called for rebels to be armed.
"Saudi Arabia is sending us terrorists," a resident of the devastated areas said on television.
Another said "these are the friends... of the Istanbul council," referring to the opposition Syrian National Council set up in the Turkish city last August.
An Arab diplomat told AFP that Saudi Arabia, which closed its embassy in Damascus this week, was delivering military equipment to Syrian rebels.
"Saudi military equipment is on its way to Jordan to arm the (rebel) Free Syrian Army," the diplomat said, on condition of anonymity. "This is a Saudi initiative to stop the massacres in Syria."
Jordan rejected the report.
"Jordan categorically denies the report," government spokesman and information minister Rakan Majali told AFP. "This is completely baseless."
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Iraq, another neighbour of Syria, has informed Tehran it will not allow arms shipments to the country to pass through or over its territory, Baghdad government spokesman Ali al-Dabbagh said on Saturday.
The United States has said it was concerned that Iranian cargo flights over Iraq to Syria could be carrying arms to help Damascus crush protests.
Tehran on Saturday condemned the Damascus blasts, blaming them on unnamed countries supplying arms to Syrian rebels, Iran's official IRNA news agency reported.
On Friday, UN-Arab League peace envoy Annan warned of a regional "escalation" of the Syria conflict and urged the UN Security Council to close ranks to put pressure on Assad.
The former United Nations chief, who met Assad in Damascus last weekend, has ordered a team of UN experts to Syria to discuss a possible ceasefire and international monitoring mission, his spokesman said.
Permanent Security Council members Russian and China have twice vetoed Security Council resolutions on the Syrian crisis that they said were unbalanced.
Russian Foreign Minister Sergei Lavrov said on Saturday he had spoken to Annan shortly after his talks with Assad and had been told that the strongman's resignation was not under discussion.
Annan himself told the Security Council he had had a "disappointing" response from Assad so far to his proposals.
Syria's foreign ministry said the country would cooperate with Annan and at the same time pursue its crackdown on "armed terrorist gangs" it blames for the bloodshed.
Thousands of anti-government protesters called on Friday for foreign military intervention as the Syrian Observatory for Human Rights said at least 18 people were killed nationwide.
In London on Saturday, British photographer Paul Conroy -- wounded in a bombardment in Homs last month that killed his Sunday Times colleague Marie Colvin and French photographer Remi Ochlik -- also urged military intervention.
"It's about life and death now. We must put enclaves in place, defend them from the air and the ground and save lives. Diplomacy, I'm afraid, has had its chance. It's failed," Conroy told the BBC.
In Washington, thousands of protesters gathered outside the White House to demand that the United States "stop the massacre in Syria."
The Britain-based Observatory said funerals were held on Saturday for two people killed during a Friday protest at Al-Raqqa in the northeast and security forces opened fire on mourners, killing another two people.
Huge rallies in support of Assad were held in Damascus and other major cities on Thursday to mark the first anniversary of the uprising that monitors say has cost more than 9,100 lives in 12 months.
Apart from Annan's technical team, the UN and the Organisation of Islamic Cooperation are to send experts to Damascus on a Syrian government-led humanitarian mission to protest cities devastated in shelling by security forces.
The team members will head to Damascus from New York and Geneva on Monday, Annan's spokesman said.