Property stocks dragged Dubai's index to a lower close after Emaar Properties said it was not investing in a Saudi project.
Emaar fell 5.7 percent, Deyaar dropped 3 percent and construction firm Arabtec slid 4.1 percent. Emaar's value fell after it announced on Sunday that it was not investing in a mega project by Kingdom Holding, to include the world's tallest tower. Kingdom fell 2.7 percent, wiping out most of its gains this week.
Emaar shares had surged 7.18 percent a day after Kingdom Holding said it had appointed Emaar for the project, with a total investment of at least 100 billion riyals ($26.7 billion).
In Dubai, Union Properties dropped 6.3 percent after its chief executive resigned. The index fell 2.5 percent to 2,143 points.
"Dubai could test its next support level at 2,000 to 2,050 points, with bullish investors accumulating at lower levels, while from the other side there are a lot of investors taking profit," said Sherif Abdelkhalek, Beltone Financial institutional trading manager.
He said the Dubai index was likely to retreat in the medium term, trading in a range between 1,750 and 2,100 points in July and August.
Abu Dhabi's index also ended lower, sliding 1.4 percent to 2,923 points.
Emirates Telecommunications Corp (Etisalat) fell 2.3 percent, while banks were the big losers, with National Bank of Abu Dhabi dropping 4.9 percent and Abu Dhabi Commercial Bank each declining 4.9 percent.
Saudi Arabia's index ended lower for the first session in five. The index slid 0.8 percent to 6,050 points as volumes fell by almost a third from the day before.
Emaar the Economic City was the most traded stock as it falls 1.7 percent.
Bank Muscat surged to lift Oman's index to a higher close after Oman's central bank said the lender was less exposed to two troubled Saudi companies than other regional banks.
Bank Muscat climbed 4 percent, helping the benchmark climb 1 percent to 5,653 points, its first advance for three sessions.
A late rally helped Kwuait's index end higher for the second straight session after Boubyan Bank surged on the sale of a stake in the lender to National Bank of Kuwait (NBK).
The latter rallied in the final few minutes of trading to end unchanged. It fell in early trading after after a legal row erupts over its purchase of the Boubyan stake from Commercial Bank (CBK).
CBK was unchanged and Boubyan surged 8.2 percent. The latter is also the most traded stock, accounting for around a sixth of all shares changing hands.
Kuwait's index climbed 0.3 percent to 8,309 points.
Qatar's benchmark ended lower, falling 1 percent to 7,292 its second decline in three sessions.
Industries Qatar was the main drag, falling 1.3 percent, together with Qatar Commercial Bank, which dropped 2.3 percent.
Bahrain's index ended higher, climbing 0.5 percent to 1,594 points, its second straight rise.
Emirates Telecommunications Corp (Etisalat) fell as investors cashed in gains from Sunday's seven-month closing high on the Abu Dhabi index.
Etisalat slid 1.4 percent, Aldar Properties dropped 1.8 percent and National Bank of Abu Dhabi lost 1.8 percent.
"Abu Dhabi is following the same trend today as Dubai, but is under less selling pressure," said Sherif Abdelkhalek, Beltone Financial institutional trading manager.
"Most investors are saying the UAE markets can continue to go up ufther, but I think we could be near the peak of this uptrend and I doubt Abu Dhabi can much further than 3,000 points or maybe 3,100."
The index fell 1.1 percent to 2,931 points.