TIMELINE: Zimbabwe's decade of crisis

(Reuters) - Zimbabwe's Robert Mugabe, in power since 1980, faces a tough challenge in Saturday's presidential vote being held alongside parliamentary and municipal ballots.

Following is a chronology of Zimbabwe's decade of troubles:

1998 - An economic crisis marked by high interest rates and inflation provokes riots and increasing support for the Zimbabwean Congress of Trade Unions headed by Morgan Tsvangirai.

1999 - The opposition Movement for Democratic Change (MDC) is formed and Tsvangirai is appointed leader.

2000 - Voters back the MDC and turn down a proposed constitutional amendment which would have given the president more power.

-- Mugabe's ruling ZANU-PF wins a parliamentary election amid charges of fraud and vote-rigging by the opposition.

-- Thousands of independence war veterans and their allies, backed by the government, seize white-owned farms, saying the land was illegally appropriated by white settlers.

2001 - Government agrees to stop often violent land invasions in exchange for British funds to finance land reform. Mugabe later rejects criticism he has ignored the deal.

2002 - Mugabe wins election pitting him against Tsvangirai. Observers condemn poll as flawed and unfair. Commonwealth suspends Zimbabwe.

2003 - IMF begins steps to expel Zimbabwe over dues unpaid since 2001. Commonwealth summit agrees to continue suspension, leading Mugabe to pull Zimbabwe out of the organization.

2004 - High Court acquits Tsvangirai of plotting to assassinate Mugabe and seize power, a ruling condemned by the government. Remaining charges are dropped in August 2005.

2005 - ZANU-PF wins parliamentary election, giving it the majority it needs to change the constitution.

-- About 700,000 people lose their homes or livelihoods in the demolition of urban slums.

2007 - Tsvangirai says he was badly beaten after he attempts to attend a banned protest rally, spurring international condemnation of Mugabe's government.

2008 - Mugabe announces presidential and parliamentary elections for March 29, 2008.

-- Ruling party member and former finance minister Simba Makoni launches election challenge to Mugabe and is expelled from party.

-- Tsvangirai accuses Mugabe of abusing his position to try to rig the vote.

(Writing by David Cutler, London Editorial Reference Unit)