OPEC's oil output rose in April to close to the highest level in recent history, a Reuters survey found on Friday, as production increases led by Iran and Iraq more than offset a strike in Kuwait and other outages.

Top exporter Saudi Arabia, however, made no major change to output, the survey found, despite the kingdom hinting it could boost supply after OPEC and non-member nations failed to agree to freeze output at a meeting on April 17.

Oil LCOc1 has rebounded more than 75 percent from a 12-year low in January to reach $48 a barrel, helped by the freeze initiative and signs that lower prices are starting to curb higher-cost supply, despite high inventories and other persistent reminders of a glut.

"The market is massively oversupplied," said Eugen Weinberg, analyst at Commerzbank in Frankfurt. "This rally doesn't have strong legs."

Supply from the Organization of the Petroleum Exporting Countries rose to 32.64 million barrels per day (bpd) this month, from 32.47 million bpd in March, according to the survey, based on shipping data and information from sources at oil companies, OPEC and consultants.

OPEC output has surged since it abandoned in 2014 its historic role of cutting supply to prop up prices, led by higher supply from Saudi Arabia and Iraq.

OPEC meets on June 2 in Vienna and may discuss the freeze initiative again. However, OPEC officials have been encouraged by the price recovery, which may take the urgency out of a renewed attempt to forge a deal.