By Shri Navaratnam and Ranga Sirilal
COLOMBO (Reuters) - Sri Lankan security forces maintained a high level of alert on Tuesday after the Easter Sunday bombings, officials said, amid intelligence reports that Islamist militants were planning fresh attacks before the start of the holy Islamic month of Ramadan.
The head of the police ministerial security division had said in a letter to lawmakers and other officials that attacks were expected on Sunday or Monday by militants dressed in army uniform.
There were no attacks on Sunday and Monday but security across Buddhist-majority Sri Lanka remains ramped up, with scores of suspected Islamists arrested since the April 21 attacks on hotels and churches that killed more than 250 people, including 42 foreign nationals.
However, the government lifted a ban on social media platforms such as Facebook, WhatsApp and viber, a source at the president's office said. The ban had been imposed immediately after the attacks to prevent the spread of rumours.
"Security will stay tight for several days because military and police are still tracking down suspects," a senior police intelligence official said on Tuesday.
Another government source told Reuters a document has been circulated among key security establishments instructing all police and security forces across the Indian Ocean island nation to remain on high alert because the militants were expected to try a strike before Ramadan.
Ramadan is scheduled to begin in Sri Lanka on May 6.
The government has also banned women from wearing face veils under an emergency law put in place after the Easter attacks.
Authorities suspect members of two previously little-known groups - National Thawheedh Jamaath (NTJ) and Jammiyathul Millathu Ibrahim - of carrying out the attacks, although the Islamic State extremist group has claimed responsibility.
Authorities believe Zahran Hashim, the founder of NTJ, was the mastermind and one of the nine suicide bombers.
In India, police said they had arrested a 29-year-old man in the southern state of Kerala, close to Sri Lanka, for planning similar attacks there. The man had been influenced by speeches made by Zahran, the government's National Investigation Agency said in a statement.
Sri Lanka's 22 million population is mostly Buddhist but includes minority Christians, Muslims and Hindus.
(Reporting by Ranga Srilal and Shri Navaratnam; Writing by Raju Gopalakrishnan; Editing by Paul Tait and Nick Macfie)