UPDATE 1-Georgia parliament convenes, opposition stay away

(Adds diplomat comment in paragraphs 12 & 13)

By Niko Mchedlishvili

TBILISI, June 7 (Reuters) - Georgia's newly-elected parliament held its first session on Saturday, without the main opposition coalition which boycotted the chamber in protest at what it says was a rigged election.

Addressing the session, President Mikheil Saakashvili said parliament's main task was to restore Georgia's unity -- a reference to a spiralling row with neighbouring Russia over two Moscow-backed separatist regions.

Western governments are anxious to see political stability in Georgia, a volatile ex-Soviet state which lies on a transit route for oil and gas exports and which has been invited to join the NATO military alliance.

The May 21 election handed victory to Saakashvili's supporters, securing his majority in parliament. Europe's main election monitoring body said the vote only partially lived up to Georgia's commitments on democracy.

The opposition coalition on Saturday staged a protest near parliament but it did not carry out an earlier threat to block anyone from entering the building. There was a heavy police presence both inside and outside parliament.

"Anybody who enters this parliament will be a traitor," David Gamkrelidze, one of the opposition leaders told a crowd of several hundred Saakashvili opponents gathered in front of parliament.