Specialist police officers were called after a man was seen waving a machete and gas cannister through his front window in east London.
The man, reportedly suffering a mental health crisis, was at his home in High Road, Leyton, on Monday afternoon when armed police and negotiating teams were called.
No-one was believed to have been hurt, police said.
Pictures of a large emergency services presence near the scene were posted on social media.
Officers were called at around 12.14pm and closed local roads as the situation unfolded.
A Metropolitan Police spokesman said the man was understood to be alone in the property and there was no wider threat to the public.
A 41-year-old woman from Leytonstone, who asked not to be named, told the PA news agency: “They’ve got a bay-fronted window and he had the window open. You could see a (gas) can in one hand and the machete in the other, waving it all around.
“The armed police were all at the front and police were there with the dogs. I spoke to the fire brigade because I said, ‘I don’t understand why they don’t just Taser him,’ and they said, ‘They can’t Taser him because he’s got gas cans on him and the Taser gives off a spark which could then light the cans’.
“I said to him, ‘How did it all start?’
“Apparently he was threatening a lady with the machete. That’s why armed police first turned up.”
Ionut Florea came out of his grocery store when he saw the police nearby and saw a man with a knife at a downstairs flat.
He said: “There were lots of police around.
“He was opening and closing the windows to have a conversation with the police. I could see him in the house with a knife. It was a big knife.
“When the police came he started opening the downstairs windows. He was shouting and making a noise. He was bringing the knife to the window and showing it to the police.”
Mr Florea added: “I did not see him be aggressive to people.”