Russia's most popular search engine was embroiled in a scandal today as bloggers accused it of blocking images of opposition protests, while it blamed technical problems.

Bloggers complained that they typed Russian-language opposition slogans into the Yandex search engine and found that it showed only unrelated images while a rival search engine, Google, came up with images of anti-government protests.

he chief editor of Yandex, Yelena Kolmanovskaya, told the Echo of Moscow radio station on Saturday that the search engine was having technical problems and had not yet had time to load the images into the system.

In a post on Friday, blogger Igor Bigdan cited the slogan, "It's time to change places", which opposition activists used on a giant banner showing Prime Minister Vladimir Putin and jailed oil magnate Mikhail Khodorkovsky.

Today a Google.ru search brought up dozens of images of the giant banner, which activists hung on a bridge opposite the Kremlin last month, while Yandex showed unrelated images including cars and a pigeon.

Bigdan also gave the example of the slogan "a party of thieves and swindlers," which opposition blogger Alexei Navalny created for a poster competition to criticise the ruling United Russia party.

Google.ru came up with numerous images of the posters, while Yandex's first image choice was a poster for the Russian film version of children's book "Pippy Long-Stocking."

"We are waiting for your official comments, because without them, some not very pleasant thoughts come into our heads," Bigdan wrote in a post addressed to Yandex's management on Friday.

A spokeswoman for Yandex wrote back to his blog, saying that the system's algorithms had worked incorrectly.

"I can assure you that there was no censorship and could not have been," wrote the spokeswoman, Alexandra Topka.

Russia's Internet is the country's most lively forum for political discussion, with commentators and politicians writing regular blog entries, and President Dmitry Medvedev has joined them with a video blog and Twitter posts.