Indonesian hackers have targeted the Crime Stoppers website and published the purported emails and encrypted passwords of 25 government and police addresses.

The Indonesian group BlackSinChan – not a part of the international hacktivist collective Anonymous – posted a statement on Monday night revealing the supposed passwords, and suggested it had acquired more information during the attack.

The statement said: “Today we only release some email and pass only! This is a warn for Australian goverment!”

It said the attack was motivated by the revelations that Australian spies had targeted the Indonesian president’s mobile phone.

The Crime Stoppers site was taken offline while the Australian federal police and other authorities assessed the extent of the hacking.

An AFP spokesman said the force was taking the the attacks “very seriously” but added that any attack on the AFP website – which was targeted directly last night – did not compromise its internal IT network. “No sensitive information is hosted on the AFP website,” the spokesman said.

The deputy chairman of Crime Stoppers, Peter Price, told Guardian Australia he expected the site to be back up again by Wednesday at the latest.

Price described the attack as an “intimidation tactic”, saying it was more like “throwing a rock through a shop window rather than robbing the shop itself”. He said no classified information had been hacked but would not give details on how far into the system the hackers had reached.

“The most important information sits behind a federal government firewall,” he said. “This is monitored and protected by the Department of Defence. There was no penetration to that at all.”

Price said there was “nothing classified” about the emails and passwords that had been hacked.

An AFP spokesman said it was aware some third-party login details of an AFP member had been posted online but this would not compromise internal networks.

Since Guardian Australia and the ABC revealed that Australian spying authorities had targeted the personal mobiles of the Indonesian president, his wife and eight of his inner circle, there have been a number of hacking attempts from Indonesia on important Australian sites.

Last week Indonesian hackers attacked the websites of the AFP and the Reserve Bank of Australia.

The ABC reports that a letter from Tony Abbott to Susilo Bambang Yudhoyono, responding to the president’s demand for an official explanation of the spying revelations, was hand delivered to the presidential palace in Jakarta by the former Australian army chief Peter Leahy.

Abbott had decided upon the personal delivery to ensure the letter was “conveyed with the utmost respect, befitting the importance of the subject matter and his high regard for President Yudhoyono", Leahy said.

It is unclear if the letter was handed personally to the president, who is in Bali, or if it was delivered to the palace in Jakarta.

Indonesia has officially downgraded its relationship with Australia in the wake of the phone tapping scandal, suspending all co-operation on efforts to target people smuggling as well as cancelling all joint military exercises.

Yudhoyono described Abbott’s response to the phone tapping revelations as “belittling”.

The Australian foreign minister, Julie Bishop, said she believed Abbott's letter would calm the ongoing diplomatic crisis.

“We will work very hard to build on the relationship that already exists,” she said.

She confirmed she had been in contact with her Indonesian counterpart, Marty Natalegawa, since the publication of the revelations about phone surveillance.