Sri Lanka’s military launched a major hunt on Saturday for remnants of an extremist group which carried out the Easter suicide bombings that killed 258 people, officials said.

Several Colombo suburbs were targeted by troops using emergency powers on arrests and detentions adopted after the April 21 attacks.

“Special cordon-and-search operations are under way in three areas just outside Colombo,” a military official told reporters.

Similar operations were also carried out in the country’s north-west, where anti-Muslim riots this month left one man dead and hundreds of Muslim-owned shops, homes and mosques destroyed.

Security forces have arrested scores of suspects in connection with the bombings and over what appeared to be organised violence against the island’s Muslim minority.

While authorities say the immediate jihadist threat has been blunted, President Maithripala Sirisena on Wednesday extended for one month the 30-day state of emergency imposed after the suicide bombings.

Sirisena said the move was to maintain “public security,” with the country still on edge after the attacks on three hotels and three churches that were blamed on a local extremist group, the National Thowheeth Jama’ath (NTJ).

Daesh has also claimed a role in the attacks.

Christians make up 7.6 per cent and Muslims 10 per cent of mainly Buddhist Sri Lanka.