Ukrainian police have interrupted a government session being broadcast live on television and detained Emergency Situations Service head Serhiy Bochkovskiy and his deputy Vasyl Stoyetskiy, leading both officials away in handcuffs.
Interior Minister Arsen Avakov said the two were being investigated on suspicion of corruption connected to offshore companies.
Prime Minister Arseniy Yatsenyuk suggested the men had undermined Ukraine amid economic troubles and a conflict with Russian-backed separatists.
"When the country is at war and when we are counting every penny, they steal from people and the state," Yatsenyuk said.
Yatsenyuk warned, "This will happen to everyone who breaks the law and sneers at the Ukrainian state."
He tweeted images of the detentions.
The detentions came hours after President Petro Poroshenko signed a decree dismissing powerful tycoon Ihor Kolomoyskiy as governor of Dnipropetrovsk, another signal from Kyiv that officials must stay in line for the sake of the country's security and stability.
Kolomoyskiy's dismissal followed disputes about control over state oil companies and allegations he used private armed forces to promote his interests.