South Korea's ruling party breathed a sigh of relief Thursday after a stronger-than-expected showing in local elections seen as a referendum on President Park Geun-Hye's handling of April's ferry disaster that killed about 300 people.

Despite fears of a voter backlash, Park's Saenuri Party managed to win eight of the 17 main contests for city mayors and provincial governors.

The main opposition New Politics Alliance for Democracy (NPAD), which had urged voters to register their dissatisfaction with Park's response to the Sewol ferry tragedy, took nine.

"I don't think either side can really claim much of a victory," said Choi Jin, head of the Institute for Presidential Leadership.

"The opposition was hoping for more but, given Park's high ratings before the Sewol disaster, it's still done better than it would have expected two months ago," he added.

Park's administration was sharply criticised over the Sewol disaster and the polls were the first real opportunity to measure the severity of the political impact on a national level.

As well as retaining posts in its traditional regional strongholds, the Saenuri Party managed to win a number of battleground contests in Incheon city and Gyeonggi province.

"We put up a good defence even in the midst of the Sewol disaster," party secretary general Yoon Sang-Hyun told reporters.

In a statement, the presidential Blue House said it "humbly" accepted the election outcome.

The high popularity ratings Park has enjoyed since taking in office in February 2013 have been hammered by the sinking of the 6,825-tonne Sewol on April 16 -- the defining moment of her presidency so far.

Overcoming public anger

Initial investigations exposed a culture of institutional negligence, greed and incompetence that contributed to the scale of the tragedy, most of whose victims were schoolchildren.

Although these problems have roots stretching back decades, Park and her officials became a default focus for much of the public grief and anti-establishment anger.

As a result, local issues were largely pushed aside in Wednesday's elections, as the rival parties concentrated on attacking and defending the president's reputation.

While the NPAD asked voters to hold Park responsible, the ruling party urged them to support the president's vow to overhaul the country's safety infrastructure.

With emotions still running high over the Sewol, some had expected a particularly strong turnout.

But a provisional figure of around 56.8 percent was only slightly up from 54.5 percent in 2010.

NPAD co-chairman Kim Han-Gil said it was now time for all parties to work together to "wipe away the despair" South Koreans felt following April's tragedy.

If the NPAD was disappointed that the hoped-for backlash never really materialised, there was some consolation in its victory in the election's most high-profile race for Seoul city mayor.

The popular incumbent Park Won-Soon won comfortably over his Saenuri Party challenger to hold on to what is seen as the most powerful political office outside the central government.

"My election is the victory of all citizens who, in their grief over the Sewol, demanded fundamental change," Park told celebrating supporters.

The office of Seoul mayor has taken on extra importance since former president Lee Myung-Bak used it as a springboard for his successful run to the Blue House.

Although Park has insisted he will see through his full term, there is widespread speculation that he will seek the NPAD presidential nomination in 2017.