By Aliza Marcus

ISTANBUL, July 23 (Reuter) - Turkey's parliament approved a package of amendments to the military-era constitution on Sunday, acting on promises to introduce democratic reforms European countries demand for approving a lucrative customs deal.

The amendments, which will expand political participation and lift some restrictions on unions, are part of a democratisation programme Prime Minister Tansu Ciller unveiled over one year ago.

She hopes the reforms will convince Europeans that Ankara is serious about ending human rights violations, paving the way for the European Parliament to approve later this year the customs union between Turkey and the European Union.

But European governments may argue that Turkey has yet to tackle the more complex problem of human rights, such as lifting restrictions on freedom of expression, taking steps to end torture and recognising Kurdish cultural and political rights.

Despite Ciller's promise to relax laws limiting freedom of expression, there appears to be no agreement on removing article 8 of the anti-terror law, used mainly against people who argue for broader Kurdish political and cultural rights.

Scores of writers and others are in jail for publishing books about modern Kurdish history, criticising alleged human rights abuses in the mainly Kurdish southeast or expressing Kurdish nationalist sentiments.

Hardliners in the parliament -- and within Ciller's own True Path Party -- reject changing article 8, arguing it would only encourage the 11-year Kurdish guerrilla war for independence or autonomy in southeast Turkey.

While Western diplomats have stressed the need for Turkey to take concrete steps to protect human rights, they also have said any reform would be welcomed.

The changes to the 1982 constitution -- a legacy of Turkey's 1980-1983 military rule -- were approved by 360 MPs in an early morning vote after weeks of political infighting. They will take effect after being signed by President Suleyman Demirel.

The amendments expand political participation by lowering the voting age to 18 from 20 and allowing associations and unions to get involved in political activities.

A paragraph praising the 1980 military takeover was removed from the constitution, the number of parliamentary seats was raised to 550 from 450 and MPs will be able to switch parties.

Although civil servants were given the right to collectively negotiate, they cannot strike, and union leaders have said the changes do not sufficiently broaden union rights to bring Turkey up to International Labour Organisation standards.

MPs also dropped an amendment that would have allowed people to open cases against the 1980-1983 military rulers.

The fight over the constitutional changes reflected the problems Ciller's coalition has faced in trying to back up promises to bring Turkey's laws in line with the West.

Although the amendments were widely supported by the Turkish public, Ciller had trouble amassing sufficient backing from MPs in the first round of voting, causing her initially to suspend debate during the second round.

Political analysts had said some MPs were reluctant to give Ciller a victory that would raise her political stature.

Ciller blamed the leading opposition Motherland Party (ANAP) for voting against the changes. ANAP's 97 seats were crucial to the coalition -- with 248 seats -- for the two-thirds majority needed for automatic acceptance of constitutional amendments.