(Edits)

Oct 7 (Reuters) - Turkey expects accords to normalise ties with Armenia to be signed on Saturday in Switzerland in a step towards ending a century of hostility.

Here are some details on why relations have been marred.

* NAGORNO-KARABAKH:

-- Turkey has kept its land border with Armenia closed since the early 1990s in protest at Yerevan's backing for Nagorno-Karabakh, a slice of territory belonging to ally Azerbaijan which is populated by ethnic Armenians. Ethnic Armenians in Nagorno-Karabakh, backed by Armenia, fought a war in the 1990s to throw off Azerbaijan's control over the mountain region. Some 30,000 people had been killed by the time the war ended in 1994.

-- Turkey has said it hopes to open its border with Armenia by the end of 2009, but progress in Ankara-Yerevan talks have been complicated in the past by the Nagorno-Karabakh dispute.

* SOME HISTORY:

-- In the late 19th century the Armenian minority, numbering an estimated 2 million, in the Ottoman Empire were encouraged by exiled groups in the United States, Geneva and in the Georgian capital, Tbilisi, to assert their nationalism.

-- Repression by Ottoman irregulars, mainly Kurds, led to the massacre of some 30,000 Armenians in eastern Anatolia in 1894-1896. Several thousand more were killed in Constantinople in August 1896 after Armenian militants seized the Ottoman Bank. Massacres were stopped after the Great Powers threatened to intervene.

* WHAT HAPPENED IN 1915:

-- As the Ottomans fought Russian forces in eastern Anatolia during World War One, many Armenians formed partisan groups to assist the invading Russian armies.

-- On April 24, 1915, Turkey arrested and killed hundreds of Armenian intelligentsia.

-- In May 1915, Ottoman commanders began mass deportation of Armenians from eastern Turkey thinking they might assist Russian invaders.

-- Thousands were marched from the Anatolian borders towards Syria and Mesopotamia (now Iraq) and Armenians say some 1.5 million died either in massacres or from starvation or deprivation as they were marched through the desert.

* DIFFERING VIEWS:

-- Ankara has said large numbers of both Christian Armenians and Muslim Turks were killed during the violent and chaotic break-up of the Ottoman Empire. A law in Turkey makes it a criminal offence to call the killings a genocide.

-- Armenia insists the killings should be declared a genocide. President Serzh Sarksyan said in a speech to mark Armenia's annual Genocide Day that securing international condemnation of the killings would be a priority for his administration.

Sources: Reuters/Dictionary of Twentieth Century History.

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