Taiwan President Tsai Ing-wen has apologized to the public over the weekend for a smuggling scandal that has overshadowed her just-concluded foreign trip.

"As a national leader, I must apologize for not discovering the longstanding practice earlier and correct the wrongs," Tsai said Saturday.

However, the main opposition Nationalist Party (KMT) described the incident as outright corruption and a national security issue. The party's legislative caucus has petitioned to the Control Yuan, asking the government watchdog to look into the matter.

Tsai apologized one day after she angered many by describing the attempt by members of her entourage to smuggle duty-free cigarettes as an "excessive purchase," leading some to question her government's resolve to fix the problem.

Tsai said although it is a longstanding practice, she wanted the Taiwanese public to know that her government will get to the bottom of the matter.

Some observers viewed her apology as a way of putting the matter to rest ahead of January's presidential election.

Upon returning from her 12-day state visit to four of Taiwan's diplomatic allies in the Caribbean on July 22, two members of her security detail were accused of trying to smuggle about 10,000 cartons of cigarettes duty-free into Taiwan, using her trip as a cover.

Acting on tips provided by New Power Party Legislator Huang Kuo-chan, the Customs Administration intercepted five trucks loaded with the cigarettes, which were following Tsai's motorcade from the airport.

National Security Bureau agent Wu Tsung-hsien, who accompanied Tsai on the trip, allegedly purchased a total of 10,009 cartons of cigarettes.

The cartons were kept in a warehouse of China Pacific Catering Services, a firm affiliated with China Airlines, at Taiwan Taoyuan International Airport, awaiting pick-up when Wu returned from the trip.

Wu and Chang Heng-chia, another presidential security staffer suspected of involvement in the scandal, have been detained for questioning.

After the news broke, National Security Bureau head Peng Sheng-chu tendered his resignation and Chang Chieh, chief aide-de-camp to the president, was transferred and received one major and two minor demerits.

Tsai has asked Peng's successor, Chiu Kuo-cheng, to complete an investigation report within a week.

China Airlines, which has been managing presidential chartered flights since the 1990s, also found itself embroiled in the scandal.

Company Chairman Hsieh Shih-chien has apologized for mismanagement and promised that the airline would not accept pre-flight orders of duty-free cigarettes and that cigarette purchases will be limited to one carton per person.

The airline also meted out punishments, including demoting its senior vice president Lo Ya-mei and vice president of the chartered flight division Chiu Chang-hsin, among others.