Dutch engineer Johannes van Damme, was hanged just before dawn at Changi Prison, his final appeals rejected only hours earlier.
Singapore Foreign Minister and Law Minister Shanmugam Jayakumar on Friday defended the decision to go ahead with the execution.
Speaking in Germany at a conference of foreign ministers from the European Union and the Association of Southeast Asian Nations, Jayakumar said the credibility of the judicial system depended on the implementation of judgments.
"I ask for understanding but laws have to be respected," he said at the opening of the two-day conference.
German Foreign Minister Klaus Kinkel earlier told reporters that as chairman of the European Union Council of Ministers, he had made a last-ditch attempt on Thursday night to persuade the Singapore authorities to spare van Damme's life. "Unfortunately I did not succeed," said Kinkel.
Jayakumar said 76 people, half of them foreigners, had been hanged in the city-state since the death penalty for drug offenses was imposed in the 1970s.
Jayakumar said there had been no protests over previous hangings of foreigners.
Van Damme was the first Westerner to hang for a drug offence. He was arrested in the transit lounge at Singapore airport on Sept. 27, 1991. A checked-in suitcase of his had 4.32 kilograms of heroin inside.
In Singapore, possession of more than 15 grams of heroin is punishable by death.
Since van Damme's conviction for drug trafficking in April, 1993, the Dutch government has repeatedly appealed on humanitarian grounds, including pleas by its prime ministers and its queen.
Despite consistent rejections of those earlier appeals, Dutch Foreign Minister Hans van Mierlo said in The Hague on Tuesday: "We will leave no stone unturned in our efforts to prevent this sentence being carried out."
On Wednesday, according to a statement he issued after the hanging, he said that "I wrote to my counterpart in Singapore, requesting him to arrange for postponement of the execution."
On the same day van Damme's lawyer, who had already made previous appeals that were rejected, filed a last-ditch application for a stay of execution.
The World Council of Churches and Amnesty International also made appeals for the sentence to be commuted. The latter this week urged its members to send pleas for clemency to Singapore.
"The government will get a lot of messages," a spokeswoman for Amnesty's Dutch branch said Wednesday.
Until Friday, Singapore's government maintained near total silence despite the intense Western diplomatic pressure and media attention, although it did confirm receipt of the lawyer's appeal.
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