KYIV, Ukraine (AP) -- Ukraine's anti-corruption agencies said they had uncovered a major graft scheme involving inflated military procurement contracts, just two days after Ukraine's parliament voted to restore the agencies' independence.

In a joint statement published Saturday on social media, the National Anti-Corruption Bureau (NABU) and the Specialized Anti-Corruption Prosecutor's Office (SAPO) said the suspects had taken bribes in a scheme that used state funds to buy drones and other military equipment at inflated prices.

"The essence of the scheme was to conclude state contracts with supplier companies at deliberately inflated prices," the statement said, adding that offenders had received kickbacks of up to 30% of the contracts' value.

The anti-corruption bodies did not identify the detainees, but said a Ukrainian lawmaker, local district and city officials, and National Guard servicemen were involved. Four people have been arrested so far, they said. The Interior Ministry said the National Guard personnel implicated in the case were removed from their positions.

Drones have become a crucial asset in modern warfare for both Ukraine and Russia, enhancing military reconnaissance, precision strikes, and strategic flexibility on the battlefield. The majority of Russian military assets destroyed by Ukrainian forces, including manpower and heavy weaponry, have been targeted by drones. Drone production is also a key aspect of Kyiv's hopes to expand domestic military production and export markets.

Ukrainian President Volodymyr Zelenskyy addressed the development in his nightly address on Saturday, calling the graft scheme "absolutely immoral" and thanking the anti-corruption agencies for their work.

"Unfortunately, these corruption schemes involved the procurement of electronic warfare systems and FPV drones ... There must be full and fair accountability for this," he said in his address, posted to X.

In an earlier post, which also included photos of him meeting with the agency heads, Zelenskyy said it is "important that anti-corruption institutions operate independently," adding that "the law passed on Thursday guarantees them all the tools necessary for a real fight against corruption."

The exposure of the graft scheme by NABU and SAPO came just two days after Ukraine's parliament voted to restore their independence.

Ukraine's Parliament on Thursday overwhelmingly approved the bill presented by Zelenskyy, reversing his earlier contentious move that curbed their power and sparked a backlash, including street protests, a rarity in wartime.

Last week's measure to place the watchdogs under the oversight of the prosecutor-general prompted rebukes from Ukrainians, the European Union and international rights groups. It raised fears that the government could meddle in investigations and potentially shield its supporters from scrutiny.

Fighting entrenched corruption is crucial for Ukraine's aspirations to join the European Union and maintain access to billions of dollars of vital Western aid in the all-out war, now in its fourth year. It's also an effort that enjoys broad public support.

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Morton reported from London.