keep silence or hold silence
They kept/hold a two minute silence in honour of the country's fallen soldiers.

Question

keep silence or hold silence
They kept/hold a two minute silence in honour of the  country's fallen soldiers.

Answer

Note that “holding silence “ is used for a memorial, not for something general like “keeping quiet”. And the more common way to describe that in the US would be “to observe a moment of silence”. (Don’t ask me why!)

Answer

'Held' is the most common. I have heard 'kept' being used too. 
'Hold' and 'keep' in the present tense.