Russian Foreign Minister Sergei Lavrov has said Moscow considered the shelling of its embassy in Damascus as a terrorist act.

Mr Lavrov said: "This is an obvious act of terrorism, probably aimed at intimidating supporters of the fight against terrorism."

HIs comments came ahead of talks with the UN's special envoy for Syria, Staffan de Mistura.

Two shells were fired at the Russian embassy in Damascus during a demonstration in support of Moscow although there were no immediate reports of casualties or damage to the building.

Mr Lavrov also said Russia was supporting De Mistura's efforts to ensure a political settlement to the Syria crisis and was disappointed by US reluctance to coordinate the efforts of all sides involved in fighting terrorism in Syria.

Meanwhile, Russia is not striving for leadership over Syria, President Vladimir Putin said, adding that existing cooperation with Western countries over the Syrian conflict was not enough.

Mr Putin added that Russia, the US and Europe should encourage political dialogue between the warring sides of the Syrian conflict.

Mr Putin also said Turkey was one of Russia's most important partners and Russia needed to understand how to build relations with Turkey to fight terrorism.

On the ground in Syria, insurgents are deploying more men and weapons, including significant quantities of anti-tank missiles, to resist ground attacks by the Syrian army and its allies, backed by Russian air strikes, rebels and a monitoring group said.

With help from Lebanon's Hezbollah and Iranian soldiers, Syria is trying to drive insurgents from western areas that are crucial to President Bashar al-Assad's survival, and has recaptured a number of towns in the provinces of Hama and Latakia.

The Syrian Observatory for Human Rights, a British-based group tracking the war, said a battle continued for control of the town of Kafr Nabuda in Hama province, which the army said it captured on Monday. At least 25 fighters on the government's side were killed, it said.

The Observatory's director Rami Abdulrahman identified most of the reinforcing fighters as members of jihadist groups.

"The (rebel) reinforcements stopped the regime from taking Kfar Nabuda," he said.

A number of rebel groups backed by Assad's foreign enemies and operating under the banner of the Free Syrian Army have deployed anti-tank missiles along a frontline stretching from Kafr Nabuda to the town of Maan some 20 miles to the east, said Fares al-Bayoush, a former Syrian army colonel who heads the Fursan al-Haq group.

The aim is to stop government forces advancing north from Morek to rebel-held Khan Shaykhoun, both towns on a north-south highway linking the city of Hama to Aleppo and Idlib.

The rebels have been using guided anti-tank, or TOW, missiles to hit tanks and other army vehicles. "We have an excellent supply of missiles," Mr Bayoush said.

"TOW launching platforms have been deployed along the entire frontline," he said. "We will, God willing, move to attack, not just defence."

Foreign states opposed to Assad have supplied TOW missiles to a number of rebel groups via an operations room in Turkey, one of the states in the region that wants Assad gone.