UPDATE 1-Blackout hits most of Russia's St Petersburg

ST PETERSBURG, Russia, Aug 20 (Reuters) - An electricity blackout hit most of Russia's second city, Saint Petersburg, after a failure at a local sub-station on Friday, power generator TGK-1 told Reuters.

Traffic lights were not working in the city of 4.5 million, resulting in massive traffic jams as well as the switching off of water supplies, a Reuters witness said.

State television said the electricity was cut off at 6:40 p.m. (1440 GMT). Local media said several forms of public transport had ground to a halt.

'The eastern sub-station is not working... There is no electricity in the centre of the city, the northern part and the northern suburbs,' said a spokesman for TGK-1, where Finnish utility Fortum owns a 25 percent stake.

Interfax news agency said city police had beefed up security across the city.

Russia's national power grid operator FSK said the St Petersburg nuclear power station was working normally.

(Reporting by Denis Pinchuk; Writing by Gleb Bryanski, editing by Amie Ferris-Rotman and Charles Dick) Keywords: RUSSIA/BLACKOUT ([e-mail] ; [phone]; Reuters Messaging: [e-mail] ) COPYRIGHT Copyright Thomson Reuters 2010. All rights reserved. The copying, republication or redistribution of Reuters News Content, including by framing or similar means, is expressly prohibited without the prior written consent of Thomson Reuters.