Pressure is growing on the Czech PM to quit over allegations against a close aide of his in a corruption scandal.
PM Petr Necas, 48, has denied wrongdoing and said he will not stand down after close associates were charged in a police investigation.
The head of the PM's office, Jana Nagyova, was among them. She is also accused of abuse of power. President Milos Zeman says charges are "serious".
The charges follow armed police raids on government and private offices.
Two former MPs, an ex-minister and the current and former heads of military intelligence were also detained.
'Very serious allegations'
President Milos Zeman was asked on Saturday whether the cabinet led by Mr Necas should remain in office in the wake of the charges.
"I consider the charges that have been brought to be very serious, and after hearing from the chief of police and the supreme state attorney, I am coming to the conclusion that they are based on sufficient evidence. This is an indirect but clear answer to your question," he said.
The comments were the first on the issue by Mr Zeman - a political rival of Mr Necas - since the raids on Wednesday night.
Detectives have said Ms Nagyova was suspected of bribing the former MPs with offers of posts in state-owned firms.
It is alleged this was in exchange for them giving up their parliamentary seats.
Ms Nagyova - a close colleague of the prime minister for nearly a decade - is also suspected of illegally ordering military intelligence to spy on three people.
The prime minister has rejected all the accusations against Ms Nagyova, saying: "I have no reason to think that she has committed anything illegal."
On Saturday, TOP 09 - one of the coalition partners in the centre-right government - said a court decision to keep Ms Nagyova in custody pending the investigation was complicating the situation, Reuters news agency reports.
A second coalition partner, LIDEM, said the situation was becoming "more serious by the hour", it reported.
The opposition has already warned it would press for a no-confidence vote in parliament unless Mr Necas resigns.