Negotiators are still working to persuade a pro-Palestinian protester who climbed the clock tower of Big Ben barefoot to come down safely.

So far, the man has spent more than 15 hours flying the Palestinian flag from a ledge on the Elizabeth Tower, which houses Big Ben, in the Houses of Parliament. Negotiations are expected to continue overnight.

Westminster Bridge remains closed to traffic after a standoff between emergency services and the protester, who scaled the tower without shoes, while carrying the flag.

A large crowd gathered in Parliament Square to show their support for the man on Saturday, who posted on social media at 6pm that he was safe on the ledge and would come down on his own terms when he was ready.

Emergency services used an aerial ladder platform outside the tower to raise themselves towards the man in an attempt to coax him down. A small team of negotiators then began repeatedly trying to talk the protester down, but at 10.30pm on Saturday he had not yet agreed to do so.

Two cherrypickers, an incident response unit ambulance, regular ambulances and two fire engines were still at the scene late on Saturday.

At one point, shouts of “free Palestine” and “you are a hero” could be heard from a small group of supporters behind a police cordon.

The protester posted an update on Instagram at about 6pm, filming himself threatening to climb higher if the negotiator on a platform attached to a fire engine came any closer. He said: “I will come down on my terms … Right now, I’m saying I’m safe. If you come towards me, you’re putting me in danger and I will climb higher.”

The negotiator appears concerned the protester may need food or water, or to use the toilet, and is bleeding from an injured foot. “I feel fine,” the protester said. “I’m on a large ledge here. I’m safe.”

He said he had stopped bleeding: “They’re small cuts.”

In response, the negotiator said he could see “quite a lot of blood”. Blood appears to have stained the ledge the protester is standing on.

The protester replied: “I will tell you if I’m in danger … I’m safe right now … You’re the ones putting me in danger … I’ve told you, if you come towards me, I have no choice other than to climb higher, because I’m not ready to climb down.”

The Conservative MP Ben Obese-Jecty said on X there needed to be an explanation about how the man got into the parliamentary estate.

He said: “Every day in parliament I see dozens of armed police officers patrolling Portcullis House and the parliamentary estate. Where were they today?

“On Monday there needs to be a full explanation to MPs and staff as to how this protester was able to evade security so easily.”

Parliamentary tours have been cancelled as a result of the incident, a spokesperson said.

A video thought to be filmed by the protester at 7.20am showed him climbing a fence around the Houses of Parliament.

Pro-Palestine protesters had planned to gather outside Broadcasting House, the BBC’s headquarters in central London, on Saturday. Police said the rally risked “serious disruption” to Jewish people attending Shabbat services at a nearby synagogue and imposed conditions under the Public Order Act to prevent the rally going ahead.

Protest organisers from Palestine Pulse, XR for Palestine and others moved the protest outside Downing Street, with many congregating in Parliament Square to show their support.

The Metropolitan police also restricted protest activity near Parliament Square to prevent serious disruption, with pro-Palestine protesters ordered to move from Bridge Street to Richmond Terrace.

A Met police spokesperson said: “At 7.24am on Saturday 8 March officers were alerted to a man climbing up the Elizabeth Tower at the Houses of Parliament.

“Officers are at the scene working to bring the incident to a safe conclusion. They are being assisted by the London fire brigade and the London ambulance service.”

Bridge Street, at the north end of Westminster Bridge, was closed to allow the emergency services to deal with the incident, police said. It is understood one exit of Westminster station is also closed, but there is no disruption to tube services and passengers can use other exits.

A spokesperson for the London fire brigade said: “Firefighters are responding alongside the Metropolitan police service to reports of a person scaling the Palace of Westminster.”

In the afternoon, a large crowd gathered on the corner of Parliament Square in support of the protester. Some held signs reading: “Labour Tories BBC you show Russia’s crimes but hide Israel’s … why?”

Reports suggested the protester had been overheard saying “peaceful protesters are being brutally arrested” and “I’ve brought the protest to the so-called hub of democracy in the UK” to onlookers below.

The incident came amid a weekend of pro-Palestine protests across the country. Activists targeted one of Donald Trump’s golf courses in Scotland on Saturday. Palestine Action supporters spray-painted the clubhouse at the Trump Turnberry resort and dug up some of the greens overnight.

In a video the group posted on social media, the words “Gaza is not 4 sale” are sprayed on the grass of the course.

The group said its action was a “direct response to the US administration’s stated intent to ethnically cleanse Gaza” after “having laid out plans to ‘clean out the whole thing’ and forcibly displace its population”.

A spokesperson said: “Palestine Action rejects Donald Trump’s treatment of Gaza as though it were his property to dispose of as he likes. To make that clear, we have shown him that his own property is not safe from acts of resistance. We will continue to take action against US-Israeli colonialism in the Palestinian homeland.”

PA Media contributed to this report