Brent crude futures, the international benchmark for oil prices, were at $48.55 per barrel at 0130 GMT, up 13 cents, or 0.3 percent, from their last close, Reuters said.
U.S. West Texas Intermediate (WTI) crude futures were at $46.12 per barrel, up 10 cents, or 0.2 percent.
In a sign of strong demand, data on Monday showed refineries in China increased crude throughput in June to the second highest on record.
Despite this, oil markets have struggled with oversupply since 2014, resulting in a more than 50 percent fall in prices since then.
Read alsoReuters: Oil prices rise on strong China demand, signs of U.S. output slowdownA deal by the Organization of the Petroleum Exporting Countries with Russia and other non-OPEC producers to cut supplies by around 1.8 million barrels per day (bpd) between January this year and March 2018 has so far not led to the tighter market and higher prices that producers have hoped for.
That's because supplies from within OPEC remain high largely due to rising output from Nigeria and Libya, two OPEC states exempt from the pact, and increasing U.S. production.
Ecuador, a small producer within OPEC, also said on Tuesday that it is not complying with its production cut of 26,000 bpd due to the country's fiscal deficit which is expected to hit 7.5 percent of GDP this year.
Oil Minister Carlos Perez said that Ecuador was only cutting some 60 percent of that figure, putting current output at 545,000 bpd.
"We are not meeting the quota imposed on us because of the obvious needs the country has," Perez said.