Campaigners have camped out beside one of the entrances to the ExCeL in anticipation of the Defence and Security Equipment International (DSEI) arms fair.
Activists with tents set-up beside one of the main road entrances to the west of the conference centre on Monday, September 2.
They attempted to block access to the ExCeL, with police confirming they arrested four people for allegedly obstructing the highway.
The goal was to stop military equipment being delivered to the centre in the run-up to the fair.
The first day had a focus of 'Stop Arming Israel', with UK-Israel arms exports reaching record levels in 2018, according to protest group Campaign Against the Arms Trade.
That comes as Israel's human rights record continues to be suspect, with the Human Rights Watch observing rights abuses and the illegal occupation of land in the West Bank.
Adie Mormech was at the protest and is from Manchester Palestine Action. He also said he taught English and French in Palestine and that he lost students to drone strikes.
He said: "We are seeing just pictures of screaming people over there. I know them, they're people just like us."
Other focuses by the activists will include religious groups opposing the arms trade and getting rid of nuclear weapons.
Andrew Smith from Campaign Against the Arms Trade said: "Thousands of activists and campaigners from across the UK will come together outside the Excel Centre this week. We will be united by our opposition to one of the biggest arms fairs in the world. DSEI will bring many of the world's most appalling regimes together with the biggest arms companies.
"Right now, UK fighter jets and bombs are playing a central role in the destruction of Yemen; what will be the next atrocity they are used in? War, repression and injustice are fuelled by events like DSEI. It's time to shut it down for good."
The protests come after international artist Anish Kapoor and the former Archbishop of Canterbury Rowan Williams threw their weight behind the anti-arms trade campaign last week.
The last DSEI in 2017 (the fair is biannual) saw daily blockades and more than 100 arrests.
The fair's organisers have always maintained that it only supports the legitimate arms industry and they respect the right to protest.
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