Saudi Aramco has received over $50 billion in bids for its debut international bond sale, which had been expected to be in the $10 billion region, sources familiar with the matter said.

The state-owned oil giant is marketing a U.S. dollar-denominated debt issue split into six tranches with maturities ranging from three to 30 years.

One of the sources said demand had gone up to $60 billion. That would be the highest order book value since a record issuance by Qatar last year, which attracted around $52 billion in orders.

Before opening the books earlier on Monday, the Aramco issue - which will be priced on Tuesday - had already attracted over $30 billion in demand, Saudi Energy Minister Khalid al-Falih said.