Senanayake, the first Prime Minister of the island forming a government with a coalition with his United National Party (UNP), the Sinhala Maha Sabha of S. W. R. D. Bandaranaike and the Tamil Congress of G. G. Ponnambalam.

[12] In 1965, the new prime minister Dudley Senanayake created the Dudley-Chelvanayakam Pact, which sought to find a compromise on the issues of language, colonization, and devolution.

Sinhala colonization of the Eastern Province abated and there were modest gains in making Tamil the language of administration in the north and east.

Some elements within the defeated SLFP were accused of fomenting the violence through planned and organized spreading of false rumours against Tamils to destabilize the government.

Anti-UNP political motivation was revealed by the Sinhalese rioters who reportedly told their Tamil victims that they were being punished for helping the UNP win the elections.

[21][22] Walter Schwarz in the Minority Rights Group reported:[11] The trouble began in Jaffna, capital of the Northern Province, when Sinhalese policemen, believed to have been loyal to the defeated Sri Lanka Freedom Party of Mrs Bandaranaike, acted provocatively by bursting into a Tamil carnival.

Among 1500 people arrested were several known Sinhalese extremists, accused of instigating violence against Tamils.Edmund Samarakkody in Workers Vanguard reported:[23] The outbreak in mid-August (1977) of the anti-Tamil pogrom (the third such outbreak in two decades) has brought out the reality that the Tamil minority problem in Sri Lanka has remained unresolved now for nearly half a century, leading to the emergence of a separatist movement among the Tamils.

[24] His wife Mangayarkarasi Amirthalingam emotionally recounted some incidents of rape that occurred during the 1977 pogrom and said "Tamil women could not walk the streets during nights in safety.

"[25] The following is a breakdown of the rioting by district as given in the "Report of the Presidential Commission" (1980) and other eyewitness accounts: On 12 August, four policemen visited a carnival at St. Patrick's College, where they assaulted Mr. Kulanayagam, who asked them for an entry free.

[9] On the morning of the 16th at 5am, MP V. Yogeswaran stated that a number of people came to his house to inform him that 10 policemen in Khakis had set fire to shops in the Old Market at 1.40 AM.

Sansoni states that Mr. Joseph, Additional Government Agent received a letter to the Government Agent from three Trade Unions of the Jaffna Kachcheri who complained that "the Police committed atrocities on the innocent public from last night, causing damage to public properties, Normal life has come to a standstill.

As a protest against the Police authorities the members of our Unions in all offices in the District have decided to go on strike till the issues involved are satisfactorily resolved.

[9] On the morning of 16 August, a police inspector attempted to remove the shot policeman from the hospital without following due procedure, and Sansoni speculated that this was the cause of rumors that doctors in Jaffna did not attend to Sinhalese policemen.

Some of the elders had brought used tyres, piled them up at CSK Junction and set them on fire, creating a barricade so that the Police could not come into our area.

Tamils at the Department of Health in Anuradhapura were also attacked by Sinhalese hospital employees despite some police and army protection being afforded to them.

[9] Dr. K. N. K. Wijayawardana, the Medical Superintendent at Anuradhapura hospital recounted the violence that had occurred there: '...a mob of about hundred people armed with iron rods and other weapons had broken the door of the room where the Tamil clerks had taken refuge and attacked them.

Later I learnt also that the mob after their foul murder at the hospital had planned to march to my quarters and attack the Tamil doctors and their families there.

"[20] He continued to spread these false rumours throughout the night, introducing macabre variations, such as the claim that Sinhalese women were being nailed to walls in Jaffna.

A police patrol was provided to the hospital, however the female house officers' quarters (used by a Sinhalese doctor) was burnt down before it arrived.

The police inspector had arrested some of the assailants in that case, and Tamil businessmen were sufficiently assured of their safety that they kept their shops open.

In Badulla town, a Tamil man was assaulted and his father was cut with an axe by masked assailants when the latter attempted to intervene.

[9] Taking advantage of the rioting, Tamil militants on 31 August stole Rs 26,000 from the People's Bank branch at Manipay and five rifles from the Sri Lanka Customs office in Jaffna.

Jayasinghe, Permanent Secretary to the Ministry of External Affairs and Defence; Major General Sepala Attygalle, Army Commander; Stanley Senanayake, Inspector General of Police (IGP) and Ana Seneviratne, Deputy Inspector General of Police (DIG) had arrived in Jaffna by air as a result of telephone calls made by Amirthalingam to the Prime Minister and by Navaratnam to T. B. Werapitiya, Deputy Minister of External Affairs and Defence stating that there has been rioting, Police firing and going berserk.

The authorities proposed a curfew, which was rejected by the members of parliament, who feared irresponsible police actition unobserved by the public under the cover of darkness.

Whatever it is, when statements of that type are made, the newspapers carry them throughout the island, and when you say that you are not violent, but that violence may be used in time to come, what do you think the other people in Sri Lanka will do?

[9] President William Gopallawa appointed former Chief Justice Miliani Sansoni, who had served as Chief Justice of Ceylon from 1964 to 1966, as the Commissioner of a Presidential Commission of Inquiry on 9 November 1977 to inquire and report on the events "to ascertain the circumstances and the causes that led to, and the nature and particulars of, the incidents which took place in the Island between the 13th day of August, 1977 and the 15th day of September, 1977".

A delegation of seven leading British citizens consisting of Sir John Fostor, David Astor, Robert Birley, Louis Blom-Cooper, James Fawcett, Dingle Foot and Michael Scott expressed their outrage in The Times of 20 September 1977:[37]Sir, A tragedy is taking place in Sri Lanka: the political conflict following on the recent elections is turning into a racial massacre.

They need our attention and support.More than 75,000 plantation Tamils became victims of ethnic violence and were forced to relocate to northern and eastern Sri Lanka.

The pogrom radicalized Tamil youths, convincing many that the TULF's strategy of using legal and constitutional means to achieve independence would never work, and armed struggle was the only way forward.

On 7 September 1978, Air Ceylon flight 4R-ACJ was bombed by suspected militants, which along with attacks on its security forces and informants compelled the government to pass several harsh legislation, some of which became permanent.