Kenyan Finance Minister Henry Rotich is in custody now awaiting to be taken to court. (AFP)

Kenya's Finance Minister Henry Rotich and other treasury officials were arrested Monday on corruption and fraud charges over a multi-million dollar project to build two mega dams, police said.

Director of Public Prosecutions Noordin Haji had ordered the arrest and prosecution of Rotich and 27 other top officials on charges of fraud, abuse of office and financial misconduct in the latest scandal to rock graft-wracked Kenya.

Rotich, his principal secretary and the chief executive of Kenya's environmental authority then presented themselves to the police.

"They are in custody now awaiting to be taken to court," police chief George Kinoti told AFP.

"We are looking for (the) others and they will all go to court."

Haji said the conception, procurement and payment processes for the dam project -- part of a bid to improve water supply in the drought-prone country -- was "riddled with irregularities".

"Investigations established that government officials flouted all procurement rules and abused their oath of office to ensure the scheme went through," said Haji.

He pointed to the awarding of the contract to Italian firm CMC di Ravenna in a manner that he said flouted proper procurement procedures, and despite financial woes that forced the company into liquidation and had led to it failing complete three other mega-dam projects.

According to the contract, the project was to cost a total of $450 million (401 million euros), but the treasury had increased this amount by $164 million "without regard to performance or works," said Haji.

Some $180 million has already been paid out, with little construction to show for it.

Another $6 million was paid out for the resettlement of people living in areas that would be affected by the project, but there is no evidence of land being acquired for this, the chief prosecutor said.

"I am satisfied that economic crimes were committed and I have therefore approved their arrests and prosecutions," said Haji.

"Well-choreographed scheme"

"The persons we are charging today were mandated with safeguarding our public interest and deliberately breached this trust.

"Under the guise of carrying out legitimate commercial transactions, colossal amounts were unjustifiably and illegally paid out through a well-choreographed scheme by government officers in collusion with private individuals and institutions."

Rotich has previously denied any wrongdoing in the scandal.

The dams scandal is one of several in the poverty-plagued country that has seen hundreds of millions of dollars of public money disappear due to fraud.

In 2017 Kenya fell to 143rd out of 180 countries in Transparency International's annual corruption index.

In March 2018, a damning report from the auditor general showed the government could not account for $400 million in public funds.

A string of top officials have been charged since last year as President Uhuru Kenyatta vows to combat corruption -- a refrain weary Kenyans have heard from multiple presidents.