Oil prices rose on Monday, as investors kept a close eye on a drone attack on an oil field in Saudi Arabia on Saturday, causing concerns over global supply.

The West Texas Intermediate for September delivery rallied 1.34 US dollars to settle at 56.21 dollars a barrel on the New York Mercantile Exchange, while Brent crude for October delivery rose 1.10 dollars to close at 59.74 dollars a barrel on the London ICE Futures Exchange.

A Saudi minister said a drone attack on Saturday caused a minor fire in a gas plant in an oil field in eastern Saudi Arabia, the Saudi Press Agency (SPA) reported on Saturday.

In a statement carried by the SPA, Minister of Energy, Industry and Mineral Resources Khalid A. Al-Falih said the attack on Shaybah Oil Field on Saturday morning caused limited damage with no injuries reported.

The oil production and exports wouldn't be affected by the "terrorist" attack, Al-Falih added.

The attack was part of hostilities against the international oil supply and economy, he noted.