Service tax under works contract

I have a query regarding applicability of service tax on works contract.

My company has received the invoice for getting work done of Erection/commissioning of some of its parts in factory.

The vendor has raised single invoice but in that it has separately shown the material portion & labour portion, & has charged VAT on material portion & full service tax @ 14.5% on labour portion.

In this case do we have liability to pay service tax under works contract