Two huge bomb blasts killed at least 27 people in the heart of the Syrian capital on Saturday, state media said, as international envoy Kofi Annan warned of regional fallout from the year-long bloodshed in Syria.

The early morning "terrorist" attacks, apparently car bombings timed minutes apart, targeted criminal police headquarters in the Duwar al-Jamarek area and air force intelligence offices in Al-Qasaa district, state television said.

"Twenty-seven people, mostly civilians, were killed and 97 others wounded in the two explosions," Health Minister Wael al-Halaqi said on Syria News, another official television channel.

As angry residents vented their fury at Arab supporters of anti-regime activists, he said the remains of three bodies were among the grisly toll of the early morning blasts.

The state broadcaster ran footage of a charred body inside the mangled remains of a smouldering vehicle in Duwar al-Jamarek (Customs Roundabout).

The facade of a multi-storey building was totally gutted by the impact of the other blast and several cars destroyed. The television broadcast images of wrecked apartments and blood-splattered streets.

Paris, which has been at the forefront of calls for Assad to quit, condemned the attacks.

"France condemns all acts of terrorism, which cannot be justified under any circumstances," Foreign Minister Alain Juppe said, expressing his condolences to the families of the victims.

A spate of bombings have hit Syria's big cities in recent months amid growing concerns that Al-Qaeda has taken advantage of the uprising against Assad.

The opposition has accused the regime of having stage-managed the attacks.

Commentators on state television blamed Qatar and Saudi Arabia, the fiercest Arab critics of President Bashar al-Assad over his regime's deadly crackdown on dissent since March 2011, which have both called for rebels to be armed.

"Saudi Arabia is sending us terrorists," a resident of the devastated areas said on television.

"These are the friends ... of the Istanbul council," said another, referring to the opposition Syrian National Council set up in the Turkish city last August.

An Arab diplomat, on condition of anonymity, 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. "This is a Saudi initiative to stop the massacres in Syria."

Baghdad, meanwhile, has informed Tehran that it will not permit arms shipments to Syria to pass through or over its territory, Iraqi 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, a close ally of Tehran, crush protests.

On Friday, UN-Arab League peace envoy Annan warned of a regional "escalation" of the deadly conflict in Syria 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, on a trip starting Sunday, to discuss a possible ceasefire and international monitoring mission, his spokesman said.

Russian and China have twice used their veto powers as permanent members to block 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 was informed that the strongman's resignation was not under discussion.

Annan himself told the Security Council that he has 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," which it holds responsible for the year of bloodshed.

Thousands of anti-government protesters called Friday for foreign military intervention to bring down Assad. The Syrian Observatory for Human Rights said at least 18 people were killed across the country, updating an earlier toll.

A large crowd also took part in a rare demonstration in Al-Raqqa, a city in northeast Syria, as seen in a video posted on the Internet by activists.

The Britain-based Observatory said funerals were held on Saturday for two people killed during the Al-Raqqa protest 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 this weekend on a Syrian government-led humanitarian mission to protest cities devastated in shelling by security forces.