Oil prices have increased after proof that OPEC and other key producers have been reducing output as agreed outweighed an increase in US crude inventory.

Brent crude inched up 50 cents to reach $57.30 a barrel while US light crude grew 30 cents to $54.18, reported Reuters.

US crude oil stockpiles increased by 6.5 million barrels to 494.76 million barrels, according to the Energy Information Administration.

The rise in crude stock exceeded more than analysts' expectations of 3.3 million barrels. Stockpiles in the US have been the highest for most of the past year.

Domestic production in the US is growing as firms have increased their drilling activity.

"The rise in crude stock exceeded more than analysts' expectations of 3.3 million barrels."

Last year, OPEC and other key producers agreed to cut down output by a total 1.8 million barrels per day (bpd) to push up prices.

According to a Reuters survey, the compliance level of the promised output cut is above 80%.

Oil production from Russia dropped in January by 100,000bpd, data from the country’s Energy Ministry revealed.

Tensions have escalated between the US and Iran after Tehran tested a ballistic missile. This has increased the possibility of future sanctions, which in turn could lead to a cut in oil supply.