Syrian regime defiant amid blasts

Smoke rises after an explosion was heard near the Palace of Justice in central Damascus on Thursday.

• The U.S. seeks a political transition plan in Syria, but Russia opposes the idea
• After the meeting, Clinton heads to Geneva for another gathering on Syria
• U.N. chief says he hopes it marks a "turning point" in diplomatic efforts
• Violence continues as diplomats prepare for weekend talks

(CNN) -- Explosions rocked the Syrian capital Friday morning, opposition activists said, hours before U.S. Secretary of State Hillary Clinton meets her Russian counterpart to raise pressure on the crisis in the Middle East nation.

Clinton meets Russian Foreign Minister Sergei Lavrov in St. Petersburg amid their nations' deep divisions over Syria.

The meeting is expected to include talks on Russian arm sales to Syria, the State Department said.

U.S. officials have advocated a political transition plan in Syria, but Russia opposes the idea of foreign intervention in the violence-hit nation.

After the meeting, Clinton will attend an emergency gathering led by international envoy to Syria, Kofi Annan, in Geneva on Saturday. U.N. Secretary-General Ban Ki-moon said he hopes the meeting marks a "turning point" in diplomatic efforts.

As diplomats prepared for the weekend talks, violence raged across Syria.

Several blasts hit Damascus neighborhoods Friday, according to the Local Coordination Committees for Syria, a network of opposition activists.

Syrian security forces shelled an opposition stronghold in Daraa province, destroying homes and sending residents fleeing, according to the opposition activists.

The opposition Syrian Observatory for Human Rights said more than 140 people, including 46 government forces, died in violence Thursday.

CNN cannot independently confirm the reports of casualties or violence because Syria restricts access by international journalists.

A flurry of attacks have targeted Damascus and Aleppo cities in recent months, strikes that opposition groups have blamed on the government.

President Bashar al-Assad's regime has blamed the attacks on terrorists.

Unsettled neighbors

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Syrians afraid of the unknown

The Geneva meeting will bring together top diplomats of the five permanent members of the U.N. Security Council -- China, France, Russia, the United Kingdom and the United States -- and Turkey. Envoys from the United Nations, the European Union and the Arab League are also invited.

Iran, a major ally to Syria , is not been invited to the meeting. The United States was against Tehran's presence despite Annan's position that Iran must be involved in helping forge peace in Syria.

Lavrov described Iran as an "influential player in the situation," saying excluding it is a "great " mistake.

Russia has been under pressure to stop providing arms to the Syrian regime.

A shipment of refurbished Russian helicopters headed for Syria turned around and returned to Russia after its British insurance company dropped coverage on the ship carrying the aircraft.

Russia and China, permanent members of the Security Council, have major trade deals with Syria. Both countries vetoed a U.N. resolution calling for an end to the violence and a transition of power.

After more than 15 months, the uprising against the al-Assad regime shows no sign of abating. The Local Coordination Committees estimates about 14,000 people have died in Syria during the uprising.

CNN's Saad Abedine contributed to this report.