"We bought (stocks) worth 2 billion riyals ... we will keep investing. The market is promising," Mohamed Al-Kharashi told Reuters on the sidelines of a conference.
He said the agency invested in the bank, telecom, pharmaceutical and cement sectors.
"Our asset management strategy is 47 percent external and 53 percent internal. Our investment strategy is open both ways but we focus on maximizing internal investments," he said.
Al-Kharashi said all its investments are "secure and intact" adding the agency invested abroad in the Europe, the US and emerging markets.
Meanwhile, investor interest focused on food and agriculture stocks on Tuesday, which helped lift the Tadawul All-Share Index (TASI) 0.26 percent to 6,651.37 points.
The agriculture and food index gained 0.81 percent to 5,113.17 points. Qassim Agriculture and Food Products rose 3.1 and 10 percent respectively.
"The bulk of the activity will remain on small and mid-cap stocks, namely in the agriculture and construction sectors on pure retail speculation," said Amro Halwani, a senior trader at Shuaa Capital in Riyadh.
The value of Saudi traded shares reached SR5.27 billion on Tuesday.
Dubai's index climbed 1 percent to 1,578 points as property-linked stocks rose, with Deyaar adding 0.7 percent and Arabtec gaining 3.8 percent.
Abu Dhabi's benchmark climbed 0.4 percent to 2,651 points.
In Kuwait, Jazeera Airways and developer Mabanee lifted the benchmark, rising 5.6 and 3.5 percent respectively. The index rose 0.4 percent to 6,496 points.
Qatar's index fell to a one-week low in muted trade, dropping 0.6 percent to 8,626 points.
Oman's index hovered at 10-month lows as low buyer interest continued to plague the market. The benchmark eased 0.2 percent to 6,121 points — its lowest close since July 22 in an eighth straight decline.
The Egyptian measure gained 1.5 percent to 5,203 points.
