Saudi Arabia has withdrawn tens of billions of dollars from global asset managers as the oil-rich kingdom seeks to cut its widening deficit and reduce exposure to volatile equities markets amid the sustained fall in oil prices.

The foreign reserves of the Saudi Arabian Monetary Agency have dropped by nearly $73bn since oil prices started to decline last year as the kingdom keeps spending to sustain the economy and fund its military campaign in Yemen.

Several asset managers were hit this month by redemptions, which came on top of an initial round of withdrawals this year, people aware of the matter said.

“It was our Black Monday,” said one fund manager, referring to the large number of assets withdrawn by Saudi Arabia last week.

The latest withdrawals will be a big blow for institutions that have benefited from years of rising assets under management from oil-rich Gulf states, but are feeling the pinch after oil prices collapsed last year.

Nigel Sillitoe, chief executive of financial markets intelligence company Insight Discovery, said fund managers estimated that Sama had pulled out $50bn-$70bn over the past six months.

“The big question is when will they come back, because managers have been really quite reliant on Sama for business in recent years,” he said.

Sama’s reserves held in foreign securities have fallen $71bn in the past year, accounting for almost all of the $72.8bn reduction in overall overseas assets.

Other industry executives estimate that Sama has withdrawn even more than $70bn from existing managers.

While some of this cash has been used to fund the deficit, these executives say the central bank is also seeking to reinvest in less risky, more liquid products. “They are not comfortable with their exposure to global equities,” said another manager.