(Reuters) - Stock markets in the Middle East ended mixed on Wednesday, while the Qatari index tumbled ahead of a constitutional amendment referendum.

Saudi Arabia's benchmark index lost 0.4%, weighed down by a 1.8% fall in the ACWA Power Company, while Saudi Awwal Bank retreated 3%.

Dubai's main share index gained 0.5%, with toll operator Salik Company advancing 6.8% and Parkin Company, which oversees public parking operations in the Emirates, closing 1.7% higher.

Dubai - the regional trade and tourism hub - approved a 2025-2027 budget on Tuesday with 272 billion dirham ($74.06 billion) of expenditure, the biggest in the emirate's history, against revenues of 302 billion dirhams, its ruler Sheikh Mohammed bin Rashid al-Maktoum said in a post on X.

Sheikh Mohammed said that next year's budget would achieve an operating surplus of 21% of total revenues for the first time.

In Abu Dhabi the index added 0.2%, helped by a 2.7% increase in Aldar Properties, a day after the developer reported a sharp rise in quarterly net profit.

The Qatari benchmark dropped 1.2%, with most of its constituents in negative territory including the Gulf's biggest lender Qatar National Bank, which was down 1%.

Qatari Emir Sheikh Tamim bin Hamad Al Thani has set Nov. 5 as the date for a referendum on constitutional amendments, the Gulf country's Amiri Diwan administrative office reported on Tuesday.

The rare referendum is for citizens to vote on a set of constitutional amendments, including a proposal that would abandon an effort to introduce elections.

Outside the Gulf, Egypt's blue-chip index fell 0.8%, with Talaat Mostafa Holding losing 2.3%.

SAUDI ARABIA down 0.4% to 12,019

ABU DHABI rose 0.2% to 9,328

DUBAI gained 0.5% to 4,605

QATAR dropped 1.2% to 10,464

EGYPT lost 0.8% to 30,371

BAHRAIN was up 0.1% to 2,018

OMAN lost 0.2% to 4,756

KUWAIT added 0.1% to 7,617

($1 = 3.6729 UAE dirham)

(Reporting by Ateeq Shariff in Bengaluru; Editing by Jan Harvey)

By Ateeq Shariff