DUBAI - Saudi Arabia's stock index tumbled in early trade on Monday amid continued investor concerns about consequences from the killing of Saudi journalist Jamal Khashoggi, following fresh data that showed heavy foreign selling last week.

The Saudi index fell 1.3 percent to 7,564.49 points within half an hour, after it closed in positive territory on Sunday after surviving an early sell-off.

Saudi Arabia on Sunday described the killing of Khashoggi at its Istanbul consulate a "huge and grave mistake," but said its crown prince Mohammed bin Salman (MBS) had not been aware.

Fresh stock exchange data released on Sunday showed foreigners sold a net 4.01 billion riyals ($1.07 billion) in Saudi stocks in the week ending Oct. 18 - one of the biggest selloffs since the market opened to direct foreign buying in mid-2015.

Top U.S. lawmakers have said that they believed MBS ordered the killing, but White House officials said on Sunday President Donald Trump has not changed his belief that the crown prince is a strong leader who is passionate about his country.

Saudi's stock market has fallen more than 5 percent since Oct. 2 because of concerns the Khashoggi case could trigger U.S. sanctions against Riyadh and shrink inflows of foreign investment.

Top petrochemical producer Saudi Basic Industries Corp fell nearly 1 percent, while Al Rajhi Banking & Investment Corp dropped 1.9 percent and National Commercial Bank slumped 2.3 percent.

Dubai climbed 0.9 percent higher, buoyed by banks and real estate shares. Emirates NBD rose 2.1 percent and real estate developer Emaar Properties gained 1.4 percent.

Dubai's Mashreqbank jumped 2.9 percent after reporting a 4.6 percent rise in quarterly net profit to 587 million dirhams on Monday.

Abu Dhabi's bluechip index gained 0.1 percent, aided by a 5.8 percent jump in Agthia Group and a 1.8 percent rise in Aldar Properties.

But Abu Dhabi Commercial Bank lost 1.1 percent in light trade despite reporting a 5.5 percent rise in quarterly profit on Sunday, in line with analyst forecasts.

Qatar's stock index inched up 0.2 percent, with Ooredoo adding 1.7 percent and Qatar Islamic Insurance up 0.5 percent after reporting a double-digit jump in nine-month profit on Sunday.

But cement maker Qatari Investors Group dived 2.4 percent after the company reported a 9.3 percent drop in net profit for the same period. ($1 = 3.7518 riyals)

(Reporting by Muvija M in Bengaluru and Saeed Azhar in Dubai Editing by Mark Heinrich) ((Tom.Arnold@thomsonreuters.com; +97144536265; Reuters Messaging: tom.arnold.thomsonreuters.com@reuters.net))