The official campaigning period for the June 4 local elections kicked off Thursday amid lingering uncertainties about voter sentiment following strong public criticism of the government's handling of a deadly ferry sinking last month.

The nationwide elections for 17 new provincial governors and mayors, as well as education superintendents and local council members, are seen as a referendum on President Park Geun-hye's conservative administration.

Park, who took office in February 2013, has seen her approval ratings drop below 50 percent for the first time in more than a year amid public anger over the government's initial response to the Sewol ferry disaster.

The 6,825-ton Sewol sank off the country's southwest coast on April 16, leaving more than 300 people dead or missing. Most of the victims were students from a high school near Seoul on a field trip to the southern resort island of Jeju. All 172 survivors were rescued before the ship went under, prompting criticism that more lives could have been saved had the government acted quickly.

Amid an atmosphere of national mourning, both the ruling and opposition parties have called for low-key campaigns in order not to offend those affected by the disaster.

The official campaigning period is scheduled to run for 13 days until June 3.

Voter turnout and public sentiment among parents in their 40s are expected to be key factors in determining the elections' results, according to political analysts.

Voters could ignore the elections altogether due to disillusionment with politics caused by the ferry tragedy, or they may turn out in masses to vote in favor of the opposition bloc, analysts said.

A key point of interest is voter turnout among parents in their 40s who empathize with those who lost their teenage children in the sinking.

It also remains to be seen whether President Park Geun-hye's public apology for the government's mishandling of the disaster and her package of remedial measures, including the dissolution of the Coast Guard and a sweeping personnel reshuffle, will work in favor of the ruling Saenuri Party.

Recent public opinion polls have indicated that candidates of the main opposition New Politics Alliance for Democracy are slightly ahead of their ruling party rivals in major battleground regions such as Seoul, Incheon and Gyeonggi Province.

In the race for the Seoul mayorship, both the ruling and opposition party contenders kicked off their campaigns at midnight inside the capital's sprawling subway system.

The Seoul mayorship carries an extra weight in South Korean politics as it is often seen as a steppingstone to becoming president. Former Seoul Mayor Lee Myung-bak was elected president in 2002, running on his accomplishments as the top administrator of the city.

Ruling party candidate Chung Mong-joon, a seven-term lawmaker and son of Hyundai Group founder Chung Ju-yung, greeted passengers as he rode the subway on Line 2, stressing his pledge to improve air quality inside subway stations.

"I will consider air quality inside subway stations to be a priority to protect the lives and health of Seoul's citizens, and continue to take interest in the issue," he said.

At Cheonggu Station on Line 6, Chung helped cleaners wash the platform.

Opposition candidate Park Won-soon, who is seeking re-election after serving more than two years as mayor, started his campaign at Sangwangsimni Station, where a train collision early this month left more than 200 people injured.

"The shock and aftereffect of the recent subway accident are likely to remain with citizens and also remain with me, so I wanted to come here first as I start my election campaign," he said. "I thought that if I made another inspection, I would be able to give a sense of security to citizens." (Yonhap)