The bond sale by energy giant Saudi Aramco has attracted record demand of $85 billion from investors, one hour before bidding closed, a banking source has said. 

Saudi Arabia's Energy Minister Khalid al-Falih said the bond issue to raise $10 billion towards Aramco's purchase of a controlling stake in chemicals behemoth SABIC was already over-subscribed by three times. 

Falih is also chairman of state-owned Aramco, the world's largest energy company. 

The firm announced last month it was buying a 70% stake in SABIC from Saudi Arabia's main sovereign wealth fund, the Public Investment Fund (PIF), for $69.1 billion.

Aramco made $111 billion in net profit last year, making it the most profitable company in the world. 

It said it will pay for most of the SABIC purchase in cash.

Observers see the acquisition as way to boost the coffers of the PIF, which is leading efforts to transform the petro-state to a tech-focused economy. 

Ahead of the bond issue, Aramco revealed its accounts to international ratings agencies for the first time ever.

The firm aims to "establish a permanent presence in the world capital markets," Falih said in a clear reference that it will continue to seek debt. 

Aramco has not scrapped plans to sell up to 5% of its shares, raising tens of billions of dollars. 

Fitch ratings agency said last week that based on information received from Aramco, its planned initial public offering (IPO) still stands and is likely to take place in 2021.