In a letter that reveals a shocking level of government corruption, South Sudan President Salva Kiir is asking more than 75 former and current senior government officials to return an estimated $4 billion in stolen funds to the country.

Corruption has plagued South Sudan’s government since the 2005 peace deal that ended more than 20 years of civil war with Sudan. In January, South Sudan’s Auditor General reported that nearly $1.5 billion in government funds were unaccounted for from the 2005-06 fiscal year.

“We fought for freedom, justice and equality,” the president’s letter reads. “Yet, once we got to power, we forgot what we fought for and began to enrich ourselves at the expense of our people.”

The letter was dated May 3 and was obtained by The Associated Press over the weekend. Information Minister Barnaba Marial Benjamin confirmed its authenticity on Monday.

The president wrote that South Sudan’s citizens and the international community were “alarmed” by the levels of corruption and that “the credibility of our government is on the line.” He promised amnesty for officials who return stolen funds and to keep the identities of those officials confidential.

Despite South Sudan’s peaceful vote last year to break away from Sudan, tensions between the two sides remain, especially over what was once their shared oil industry. South Sudan this year shut down its oil industry after accusing Sudan of stealing its oil.

That decision has resulted in the loss of tens of millions of dollars for the government. Oil revenue last year accounted for about 98 percent of the government budget before the shutdown.

Kiir has stepped up efforts to fight corruption this year, and his office on Friday released a statement detailing the country’s anti-corruption efforts since the beginning of the year. The release says South Sudan has already recovered an estimated $60 million in stolen government money.

According to the statement, Kiir has reached out to heads of state in Africa, Europe, the Middle East and the United States to ask for help fighting South Sudan’s corruption.

Benjamin said that Kenya, South Sudan’s southern neighbor, is playing an active role in South Sudan’s fight against corruption. South Sudan has opened a bank account in Kenya where anyone who has taken government funds can return them.

“If anybody again is found taking government funds in an inappropriate manner, there will be laws in place that will definitely punish such individuals,” he said.”

Earlier this year Kiir issued a decree ordering all public officials to declare their assets to the South Sudan Anti-Corruption Commission. The call was supported by Vice President Riak Machar, who declared his assets to the commission in February. But the decree was initially ignored by many other officials.

The office of the president now says around 5,000 former and current public officials have declared their assets to the commission.