ALMATY, Oct 5 (Reuters) - Kazakhstan's daily crude output has fallen by about 20,000 tonnes per day this week due to lower production at the giant Tengiz field, the Central Asian nation's Energy Ministry said on Wednesday.

The ministry did not explain why Chevron-led Tengizchevroil (TCO) venture has cut production. Scheduled maintenance at the field ended last month.

"As a matter of policy, Tengizchevroil does not comment on the details of current and future production levels," the company said in an email. "Currently TCO’s production of crude oil continues uninterrupted."

TCO, in which Exxon Mobil, LUKOIL and KazMunayGaz also have stakes, is Kazakhstan's biggest oil producer. (Reporting by Olzhas Auyezov Additional reporting by Alla Afanasyeva in Moscow, Editing by Louise Heavens)