At least two people were killed in clashes last week when Sinhalese Buddhists, angered by the killing of a Buddhist driver by Muslims, attacked mosques and Muslim-owned properties in the central Kandy district.

Some of the violence was instigated by threatening posts on Facebook, according to the government, which cut access to Facebook, Viber and WhatsApp on March 7. It initially said the ban would last for three days but extended the block without informing the public, users said.

"On my instructions, my secretary has discussed with officials of Facebook, who have agreed that its platform will not be used for spreading hate speech and inciting violence," President Maithripala Sirisena said on his Twitter feed.

He said he had instructed the telecommunication regulator to remove the temporary ban with immediate effect.

Government officials have said Facebook's action against those who spread hate speech had been too slow.

"Facebook officials agreed to speed up the response time," telecommunication minister Harin Fernando, who participated in the discussion with Facebook officials, told Reuters.

"We have discussed how we can create new windows to make sure easy removal of these hate speech items," he said without elaborating.

Facebook Inc said in a statement to Reuters its officials met Sri Lankan government officials to outline the company's community standards and commitment to removing hate speech and incitement to violence from its platform.

"We have clear rules against such content, and will remove it when we're made aware of it. We are glad access to our services, and important connections for people and businesses, have been restored," the statement said.

The government lifted the ban on Viber and WhatsApp earlier this week.

Communal tensions have grown over the past year, with some hardline Buddhist groups accusing Muslims of forcing people to convert to Islam and vandalising Buddhist archaeological sites. Muslim groups deny the allegations.

Fernando said on Tuesday the government could not control hate speech and fake messages on Facebook by "extreme" Buddhists and Muslims and it had become a menace to national security.

Police are investigating whether 10 suspected ringleaders of the wave of attacks on Muslims had outside funding or foreign help.

Sri Lanka's Muslims make up about 9 percent of its 21 million people and mostly live in the east and centre of the island. Buddhist Sinhalese account for about 70 percent and ethnic Tamils, most of whom are Hindus, about 13 percent.