At least 25 people were killed and 80 wounded in twin bombings in the central Syrian city of Homs, a monitoring group said Tuesday.
Islamic State claimed responsibility for the blasts in a government-held area of Homs.
dpa could not independently verify the message posted by jihadist supporters on social media, but it is consistent with previous claims by the extremist group.
The opposition Syrian Observatory for Human Rights said 15 Syrian soldiers were among those killed in the blasts that rocked the district of al-Zahraa, whose residents are largely from the Alawite sect to which President Bashar al-Assad belongs.
Homs, a mainly Sunni city, was one of the first strongholds of the uprising against al-Assad. Alawite areas there have repeatedly been targeted by deadly attacks.
On December 16, Islamic State claimed responsibility for a car bombing also in al-Zahraa that killed 16 people.
Meanwhile, Syrian regime forces backed by Russian airstrikes seized an important town in the south of the country from rebels, state media and the Observatory said.
The capture of Sheikh Maskin comes days after major advances by government troops in the north-west and ahead of peace talks scheduled to start Friday in Geneva.
Syrian soldiers and Lebanese Hezbollah militiamen took the town, which lies between Damascus and the southern provincial capital Daraa, after fierce fighting, the Observatory said.
Almost four months of intense Russian airstrikes appear to be taking a toll on rebel resistance.
Later on Tuesday, the Syrian opposition's Higher Negotiations Committee was set to meet in Riyadh to decide its stance.
UN Syria envoy Staffan de Mistura was due to send out invitations to the Geneva peace talks, which are backed by Russia, the United States and other supporters of both al-Assad's government and the opposition.
In Moscow, Russian Foreign Minister Sergei Lavrov told a press conference that the peace talks should also include the Kurds, specifically the Kurdish Democratic Union Party.
"Without this party, without this participant, the negotiations cannot lead to the result that we want, a final political resolution in Syria," Lavrov said, according to state news agency TASS.
Turkey has opposed including the Kurds in the peace talks because Kurdish groups have been conducting a separatist rebellion in Turkey for decades.
US Secretary of State John Kerry on Monday denied putting pressure on the opposition to include the country's powerful Kurdish forces and other allies of Moscow on its negotiating team.