In 2014, violence between Muslims and Buddhists had erupted in two cities in the southern part of the country and left four people dead and 16 injured.
Sri Lanka's government imposed a nationwide state of emergency on Tuesday after a sudden spike in violence against minority Muslims in a central town, and amid fears the unrest could spread to other parts of the country. Moreover, there had been riots and arson attacks since the weekend in Kandy district.
He added, "It was also chose to take stern action against people who are instigating violence through Facebook".
Minister of National Dialogue Mano Ganeshan told Xinhua news agency that the decision had been taken following a special cabinet meeting held on Tuesday morning.
The officer said security was heightened while schools and businesses remained closed.
The emergency is a result of the clashes between Buddhists and Muslims in Sri Lanka.
Emergency in Sri Lanka post communal clashes
"The government will not hesitate to take firm and stem action against perpetrators of crimes, and those who violate the law and order", Gunawardhana added.
In a statement, Biraj Patnaik, Amnesty's South Asia director, said: "A state of emergency has been declared after two incidents of serious violence against members of the country's Muslim minority".
"We are obviously concerned over reports of the ongoing communal violence and we welcome the government's commitment to addressing the tensions and achieve reconciliation", he said.
Five persons were arrested and police said investigations are on.
That violence was instigated by a Buddhist extremist group whose leaders are on trial accused of spurring religious conflict.
Rioters damaged several muslim homes, shops and mosques. Buddhists make up about 70 percent and ethnic Tamils, most of whom are Hindus, about 13 percent.