The 45-year-old man died shortly after admission to a hospital in Puttalam district during anti-Muslim rioting which began Sunday in the area, a police official told AFP.
"Mobs had attacked him with sharp weapons at his carpentry workshop", the official said.
It was reported that they had assaulted the said person and had damaged several shops in the area.
"To control the situation, a police curfew was imposed during the night", he said.
Sri Lanka reimposed a ban on social media on Monday as religious tension flared up after an intimidating Facebook post triggered attacks on mosques and Muslim-owned businesses in the worst unrest since Easter Sunday bombings which killed almost 260 people.
One mosque suffered extensive damage, he said.
An overnight curfew was imposed in parts of northern Sri Lanka to prevent further violence.
Late in the evening on Sunday, the unrest spread to Kuliyapitiya where a mosque and a few Muslim owned shops came under attack, prompting the authorities to impose curfew in the northwest town. Earlier in the the morning, the Lankan government also reimposed a ban on social media following violent incidents between the minority Muslim and majority Sinhalese communities in the country.
Police said a mob targeted shops in the northwestern town of Chilaw on Sunday in anger at a Facebook post by a shopkeeper.
Hasmar had reportedly written, "1 day u will cry", which was interpreted as being a threat. The Islamic State claimed responsibility for the attack, but the government has blamed local Islamist extremist group, the National Thawheed Jama'ath (NTJ), for the bombings.
The main body of Islamic clerics, the All Ceylon Jamiyyathul Ulama, said there was increased suspicion of Muslims after the Easter Sunday attacks.
Internet service providers said they have been instructed by the telecommunications regulator to block access to Facebook, WhatsApp, YouTube and Instagram.
On Sunday, the Catholic Church held the first regular Sunday Mass since the attacks amid tight security.
Muslims make up around 10 percent of Buddhist-majority Sri Lanka's 21 million population and Christians about 7.6 percent.