Malcolm Turnbull and Li Keqiang.

China canceled a visit by Australian lawmakers to meet law enforcement officials in what some say is punishment for Australian interference in Chinese internal affairs in a period of deepening diplomatic tensions.

Craig Kelly, chairman of the Parliamentary Joint Committee on Law Enforcement, said Thursday he had not been given details of why he could not lead his three committee colleagues on the trip. The journey to Beijing, Shenzhen, Guangzhou and Hong Kong was to have started on Wednesday.

“The Chinese said they can’t accommodate us at this time,” Kelly told the AP. “The reasons for that are not clear.”

Australian Broadcasting Corp. reported the weeklong trip was canceled because Beijing was offended by Australia joining another 10 countries in signing a letter that questions China’s treatment of human rights lawyers.

Damien Kingsbury, a Deakin University expert on international politics, described the cancelation as a “fairly blunt message” and agreed that the human rights letter was the most likely trigger.

The controversy comes during tense diplomatic times in the Sino-Australian relationship.

Premier Li Keqiang visited Canberra last month and asked the government to ratify an extradition treaty so that Chinese fugitives from China’s anti-corruption campaign could no longer use Australia as a safe haven. The treaty was shelved a week later because it was doomed to be blocked in the Senate over human rights concerns.

Australian law enforcement authorities fear the diplomatic setback could damage cooperation with their Chinese counterparts on stopping illicit Chinese drugs such as methamphetamine from reaching Australia.

Justice Minister Michael Keenan on Wednesday praised Australia’s cooperation with China’s National Narcotics Control Bureau which he said had stopped 7.5 metric tons (8.3 US tons) of drugs from reaching Australian streets.

Kelly said his trip could not have been affected by the treaty dispute because he was told of the cancelation around the time Keqiang landed in Australia.

“I really don’t like to speculate on it,” Kelly said.

“We were meeting with Chinese politicians and law enforcement officials to see what they were doing to crack down on methamphetamine shipments to Australia,” he added.

The Chinese Embassy in Canberra did not immediately respond to a request for comment on Thursday.

Around the time Keqiang arrived in Canberra, Canadian newspaper The Globe and Mail reported that Australia, Canada, Japan, Switzerland and seven European Union countries had signed a diplomatic letter to Chinese Minister for Public Security Guo Shengkun.

The letter, dated Feb. 27, expressed “growing concerns over recent claims of torture and other cruel, inhuman or degrading treatment or punishment in cases concerning detained human rights lawyers and other human rights defenders,” the newspaper said.

Chinese Foreign Ministry spokeswoman Hua Chunying accused the countries of “violating the spirit of the rule of law” with the letter.

“We strongly oppose any country disrupting China’s judicial sovereignty and independence with the excuse of human rights,” Hua told reporters.

Human rights have caused friction in the bilateral relationship recently.

Foreign Minister Julie Bishop gave a speech in Singapore last month in which she said China can only reach its full economic potential if it embraces democracy.

Her department also made representations to Beijing over Sydney academic Feng Chongyi, who was not allowed to leave China for several days after a three-week trip researching human rights lawyers.

Australian National University international relations expert Michael Clarke said the canceled trip “would seem to be not coincidental to recent issues between Australia and China.”