Royal Dutch Shell Plc (NYSE: RDS.A) is seeking to sell its gas fields in Tunisia for about $500 million, sources said, as the Anglo-Dutch company pushes forward with its vast disposal program.

The Tunisian assets, accounting for about 65% of the North African country's gas production, were acquired as part of Shell's $54 billion take over of BG Group in 2016.

The assets include two offshore gas fields -- Miskar, fully owned by Shell; and Hasdrubal, 50% owned by Shell -- as well as an onshore production facility.

In 2015, the fields produced 30,000 barrels of oil equivalent per day, according to BG Group's annual report of the same year.

According to two industry sources and another banking source, Shell seeks to raise about $500 million from the sale.

A Shell spokeswoman declined to comment.

Shell has sold or agreed to sell more than $20 billion in assets over the past year as part of a $30 billion divestment program aimed at reducing debt following the BG acquisition.