STOCKHOLM, Sweden - The head of the Nobel Foundation yesterday rejected criticism of all-expenses-paid trips that prize jurors made to China and said it was normal for the jurors to accept such invitations.

Michael Sohlman, executive director of the foundation that manages the prestigious awards, said that he welcomed a bribery investigation into the trips and that he saw nothing wrong with them.

"When you invite a lecturer, it is normal to pay for travel and board," Sohlman said in a telephone interview. "The Nobel Foundation cannot finance such trips."

An anticorruption prosecutor opened a bribery probe last week after a Swedish Radio report that said three jurors from the medicine, chemistry and physics committees had been invited to China in 2006 and 2008 to explain the selection process and what it took to win a Nobel Prize. The Chinese paid for their plane tickets, hotels and meals, the report said.

"It happens very often that someone who is linked to the Nobels goes abroad and then they are often asked to talk about the system of awarding the Nobel Prize," Sohlman said.

The $1.2 million awards are handed out annually in six disciplines: medicine, chemistry, physics, literature, economics and peace. Each award has its own prize committee.

The committees are famously tight-lipped about their work - deliberations are kept secret for 50 years - and purport to resist outside pressure or campaigns for or against candidates.

"It is insane to let oneself be invited on trips of this kind," said Anders Barany, a former nonvoting secretary of the physics prize committee and a current voting member of the Royal Swedish Academy of Sciences.

Chinese media reports at the time said the three Nobel jurors gave lectures on the process of nominating and selecting Nobel winners.

One of them - Sven Lidin of the physics committee - said in a speech that "China and the Nobel Prizes are not far apart" and that it would not take very long for a Chinese scientist to win a Nobel, according to a report by the state-run China News Service, posted on Zhejiang University's Web site.