TIMELINE-Collapse of Sri Lanka's troubled ceasefire

(Reuters) - Sri Lanka's six-year ceasefire pact with the Tamil Tigers formally ends on Wednesday after the government decided to scrap it, arguing that the rebels were simply using it to buy time to regroup and rearm.

Following is a chronology of key incidents in the Sri Lankan civil war, which has killed around 70,000 people since it erupted in 1983:

1948 - Island of Ceylon gains independence from Britain; country is later renamed Sri Lanka.

1956 - Government makes majority Sinhala language the language of state. Minority Tamils say they feel marginalised.

1976 - As some Tamils take up arms against the state, militant Velupillai Prabhakaran forms the Liberation Tigers of Tamil Eelam (LTTE).

1983 - Tiger attack in north kills several soldiers, triggering vast anti-Tamil riots in capital, Colombo. Hundreds die, thousands flee. Start of what Tigers call "First Eelam War".

1987 - Having earlier armed Tigers, India sends troops to enforce truce. Tigers renege on pact, refuse to disarm and begin three years of fighting that kills 1,000 Indian soldiers.

1990 - India withdraws, leaving LTTE in control of northern city of Jaffna. Tigers over-run police stations in east. "Second Eelam War" begins.

1991 - Suspected Tiger suicide bomber kills former Indian prime minister Rajiv Gandhi in south India.