Nick Thorpe BBC correspondent in Bratislava

This is a critical 24 hours for Bratislava.

They are still building up defences, although the level of the river has gone down a few centimetres since it reached a peak overnight.

The city is being helped a great deal by the authorities of the Czech Republic

People are hoping that it does not rise further and inundate parts of the town.

I am standing beside the River Danube, here in Bratislava, against a great wall of sandbags in front of us.

Just to my left two policemen are just checking the water level, which at the moment is slightly less than a metre below the top of the sandbags.

In front of me I can see cruise ships moored with strong steel cables to the shore.

The water is already flowing very strongly over the gangways to those ships.

They are completely unreachable now, and several logs have been wedged up by the current against their gangways.

Streets cordoned off

Behind me, in the old town of Bratislava, there are still sandbags being built up in front of shops and businesses close to the river.

The police are still cordoning off many streets here to keep the public away from the river.

Further upstream, just a few kilometres from Bratislava, the city is being helped a great deal by the authorities of the Czech Republic, who are holding back the waters of the Morava River, just before it flows into the Danube, just as long as this flood wave passes.

So, these are the critical 24 hours for Bratislava, while this main flood wave passes the city.