Czech Prime Minister Petr Necas said Sunday he would step down amid a massive corruption scandal in which his top aide -- and alleged lover -- was indicted for bribery.

"I will step down as prime minister tomorrow. I am aware of my political responsibility," Necas told reporters after talks in Prague with partners in his centre-right minority coalition government in power since July 2010.

"When I step down the entire government will step down in line with the constitution," said Necas.

Necas said his departure "creates room for us to find a nominee" from his rightwing Civic Democrats (ODS) party for a new prime minister.

It was not immediately clear Sunday evening what action leftwing rival President Milos Zeman -- who names the prime minister under the constitution -- would take.

Zeman is allied with the leftist Social Democrat opposition party which demanded a snap election in the wake of the corruption debacle that polls show it is poised to win.

Analysts in Prague were cautious in their evaluations of whether Necas's departure meant a snap election was on the horizon.

"I'd love to know that myself," Josef Mlejnek, a political analyst at Charles University in Prague, told AFP as Necas said he would seek agreement on a new rightwing prime minister with Zeman, who has been in office since March.

The president "will be asked to show his ability to handle political crises, to come up with a solution, early elections or a government better than this one, which will be able to at least secure the operation of the state," he added.

The next regularly scheduled election is in May 2014.

Necas has led a shaky minority coalition since 2010, which has nonetheless survived eight confidence motions.

Within his rightwing Civic Democrats, deputy party chairman Martin Kuba has been tipped as a possible candidate for the prime minister's job.

"There are so many options now that I don't dare predict what it will come down to. I really don't know," analyst Mlejnek told AFP late Sunday.

Karel Schwarzenberg, chairman of the TOP 09 rightwing junior coalition party, said Sunday he hoped Necas's ODS would "generate someone who is generally acceptable.

"Of course if there's no new coalition, there will be early elections," added the aristocrat-turned-politician who lost January's presidential election to Zeman.

The graft scandal rocking Prague erupted when police earlier this week raided the cabinet office, defence ministry, villas and a bank.

Necas's chief of staff Jana Nagyova was on Friday charged with complicity in the "abuse of power and with bribery" and was placed in custody on Saturday.

Seven other people -- including military intelligence heads and former lawmakers -- have also been indicted for corruption among other alleged crimes.

The 48-year-old Nagyova was charged with bribery after allegedly promising three former lawmakers from Necas's party lucrative jobs in state-run companies on condition they quit the parliament.

But police also say Nagyova had asked Czech military intelligence to tail the prime minister's wife Radka, 47, and two other people.

Necas announced this week he was getting divorced from his wife after more than 25 years, amid media speculation that Nagyova was his lover.

An EU member since 2004, the ex-communist Czech Republic has been plagued by corruption since it emerged as an independent state after its 1993 split with Slovakia.

Corruption watchdog Transparency International in 2012 ranked the Czech Republic as worse than Costa Rica and Rwanda in terms of the prevalence of graft in its "Corruption Perceptions Index".