Fourteen security personnel from Syria’s new authorities and three armed men were killed in clashes in Tartus province after forces tried to arrest an officer linked to the notorious Sednaya prison, according to the Syrian Observatory for Human Rights.
The monitoring group said the clash broke out in Tartus, a stronghold of the ousted president, Bashar al-Assad’s Alawite minority, on Wednesday, and was sparked by the attempted arrest of the former prison official.
Related: Tears of joy and sadness as ‘disappeared’ Syrians emerge from Assad’s prisons
Syria’s new interior minister confirmed the deaths in a message on Telegram, and said 10 police officers were also wounded by what he called “remnants” of the Assad government. The minister vowed to punish anyone who dared “to undermine Syria’s security or endanger the lives of its citizens”.
On Thursday, the new Syrian military leadership said it had launched an operation to pursue the remnants of the Assad regime in the countryside of Tartus, the state news service Sana reported.
The operation had already succeeded in “neutralising a certain number” of armed men loyal to the toppled president, Sana said. The Syrian Observatory for Human Rights has reported several arrests in connection with Wednesday’s clashes.
Wednesday’s deadly incident came as demonstrations and an overnight curfew elsewhere marked the most widespread unrest since Assadfled Syria more than two weeks ago.
The demonstrations occurred around the same time that an undated video was circulated on social media that showed a fire inside an Alawite shrine in the city of Aleppo.
The interior ministry said on its official Telegram account the video dated back to the rebel offensive on Aleppo in late November and the violence was carried out by unknown groups, adding that whoever was circulating the video now appeared to be seeking to incite sectarian unrest.
In the city of Homs, Syrian police imposed an overnight curfew, state media reported, after unrest there linked to demonstrations that residents said were led by members of the minority Alawite and Shia Muslim religious minorities.
One demonstrator was killed and five others wounded in Homs “after security forces … opened fire to disperse” the crowd, Agence France-Presse reported, saying the protests were sparked by the video of the Alawite shrine.
Some residents told Reuters the demonstrations were linked to pressure and violence in recent days aimed at members of the Alawite minority, a sect long seen as loyal to Assad, who was toppled by Sunni Islamist rebels on 8 December.
Related: US lifts $10m bounty on HTS leader after talks in Syrian capital
Syria’s new ruling administration, led by the Hayat Tahrir al-Sham (HTS) group, a former al-Qaida affiliate, did not immediately respond to requests for comment on the curfew.
State media said the curfew was being imposed for one night, from 6pm local time (1500 GMT) until 8am on Thursday morning.
The Observatory also reported demonstrations by thousands in the coastal cities of Tartus and Latakia, also an Alawite stronghold, as well as other areas, including Assad’s home town of Qardaha.
The protests were the largest by the Alawites since Assad’s fall, and came after hundreds of Syrians protested in the capital, Damascus, against the torching of a Christmas tree.
The country’s new leaders have repeatedly vowed to protect minority religious groups, who fear the former rebels now in control could seek to impose a conservative form of Islamist government.
The ministry also said some members of the former regime had attacked interior ministry forces in Syria’s coastal area on Wednesday, leaving a number of dead and wounded.
Meanwhile, Syria’s new authorities torched a large stockpile of drugs on Wednesday, according to two security officials, including 1m Captagon pills, whose industrial-scale production flourished under the deposed leader.
Captagon is a banned amphetamine-like stimulant that became Syria’s largest export during the country’s civil war.
Since toppling Assad, Syria’s new authorities have said massive quantities of Captagon have been found in former government sites around the country, including security branches.