The executive board of the National Accountability Bureau (NAB) on Wednesday approved the filing of six corruption references, including one against ousted prime minister Nawaz Sharif and his younger brother Punjab Chief Minister Shahbaz Sharif.

Presided over by the Bureau's chairman, retired Justice Javed Iqbal, the board approved filing a reference against the two Sharif brothers and others over the allegedly illegal construction of a road leading to their residence in 2000, a press release said.

The Sharif brothers allegedly caused a loss of nearly Rs125 million to the national exchequer by illegally constructing a two-way road between Raiwind and the Sharif family residence in 2000, the statement said.

Former premier Nawaz is already facing trial in three corruption references filed against him by NAB on directions of the Supreme Court in the Panama Papers case. He has pleaded not guilty in all references.

Although NAB had requested the apex court to reopen the Rs1.2 billion Hudaibiya Paper Mills reference, in which both Nawaz and Shahbaz were named along with other members of their family, the appeal was rejected by SC last month.

Investigation in Nandipur power project

The NAB executive board also approved an investigation against several former ministers and government officials in the Nandipur power project scam.

Since 2012, NAB has been investigating the Nandipur power project scam which resulted in a Rs113 billion loss to the national exchequer.

In May this year, the Bureau held the law ministry responsible for the scam when Babar Awan was the federal law minister in the previous PPP government.

Besides Awan, the NAB board has approved an investigation against former water and power minister Raja Pervez Ashraf, former law secretary Pir Masood Chishti, ex-water and power secretary Shahid Rafi and former director Aijaz Bashir. They have been accused of allegedly causing delays in the project, causing a loss of Rs113bn to the exchequer.