Sydney police have arrested a man at a busy railway station allegedly carrying a small homemade bomb which he planned to detonate in the city's iconic harbour, they said on Thursday.
 
The 33-year-old was stopped and searched Wednesday evening at surburban Lidcombe railway station during a drug detection operation.
 
"The man was searched and an improvised explosive device was found inside a spectacles case," police said in a statement.
 
"The device was secured and given to personnel from the Rescue and Bomb Disposal Squad."
 
In a subsequent search of the man's home, police said they seized a gun, ammunition, spear gun and a substance believed to be methylamphetamine.
 
Inspector Barry Vincent told reporters Thursday the man allegedly planned to drop the bomb in Sydney Harbour because he was having "a bad day", although it would not have caused much harm.
 
"Certainly, in the harbour, I wouldn't expect there would be too much damage, if at all," he said.
 
"The fact he's got it with him was a concern but there was no intention to target any person or location.
 
"We will be alleging that (the man) made reference that he had a bad day."
 
The man was due to appear in court later Thursday charged with possessing an explosive in a public place and possessing a knife.