Service tax on labour contract

Dear Sirs

Please clarify whether labour contract entered into by a company for supply of manpower to execute work at their site is covered under service tax ambit.

In this case require labourers is supplied to work in the factory site and they would execute work as per the instruction of the manufacturing concern and based on the work executed the labour contractor would charge based on the nature of work, number of persons, number of hours etc.

thanking you in advance

venkatesan