Syrian troops backed by Russian air strikes are pressing ahead with an assault against rebels in central and northern Syria, according to the Syrian government and opposition activists.
The fighting is particularly intense in the central Homs province, with a fresh offensive in the northern Aleppo province.
The offensives on multiple fronts appear to be aimed at stretching rebel lines and keeping the insurgents off balance.
The Syrian Observatory for Human Rights said around 42 people were killed in air strikes and fighting in Homs province. The Local Coordination Committees, an activist network that follows the war, put the number at 57.
Russia began its air campaign on September 30, and Syrian troops and allied militia launched an ambitious ground offensive a week later.
Russian president Vladimir Putin said air strikes in Syria have killed hundreds of militants as he called for a shared military effort of ex-Soviet nations to prevent possible militant incursions to Syria from Afghanistan.
Mr Putin told a meeting of leaders of ex-Soviet nations in Kazakhstan that the Russian military has achieved “impressive” results during the air campaign in Syria.
“Dozens of control facilities and ammunition depots, hundreds of terrorists and a large number of weapons have been destroyed,” he said.
Mr Putin reaffirmed that the Russian bombing blitz against the Islamic State group and other radicals in Syria will continue “for the period of the Syrian troops’ offensive operations against terrorists”, but would not elaborate.
He said between 5,000 and 7,000 people from Russia and other ex-Soviet nations are fighting alongside Islamic State militants.
“We can’t allow them to use the experience they have just gained in Syria back home,” he said.
Russian jets have flown more than 600 combat sorties since the start of the air campaign, said Colonel-General Andrei Kartapolov, of the Russian military’s general staff.
He shrugged off the US claim that four of the 26 cruise missiles launched at targets in Syria by Russian navy ships from the southern part of the Caspian Sea had crashed on Iranian territory.
“The Pentagon may say whatever it wants,” he said. “All our missiles reached their targets.”
He said the Russian jets have not yet faced any surface-to-air missiles and warned that their use by the rebels would signal a foreign involvement.
He also reacted angrily to US defence secretary Ash Carter’s comments warning that Russia would suffer casualties in Syria and describing their operation as “highly unprofessional”.
Mr Putin, speaking in Kazakhstan, said the situation in Afghanistan is “close to critical” and called on other ex-Soviet nations to be prepared to act together to repel a possible attack.
“Terrorists of all kinds are getting increasing clout and aren’t hiding their plans of further expansion,” Mr Putin said in televised remarks. “One of their goals is to push into the Central Asian region. It’s important that we are prepared to react to this scenario together.”
He said a planned joint build-up of border guards of several ex-Soviet nations should help fend off the threats coming from Afghanistan.
Afghanistan shares a border with Turkmenistan, Uzbekistan and Tajikistan, which has been a source of drugs coming into Russia and is a long-standing worry of Moscow’s.
Mr Putin’s comments come a day after president Barack Obama announced plans to keep about 9,800 US troops in place in Afghanistan through most of next year to continue counter-terrorism missions and advise Afghans who are battling a resurgent Taliban.