Riot police were brought in to control the crowd during the weekend protests that sometimes turned violent, The Times of London reported Monday. Police officials said at least three people were arrested.
Witnesses said police removed some protesters forcibly while other demonstrators had bloodied faces.
Protesters waved Palestinian flags and held up signs reading "Holocaust in Gaza" and "No peace, No justice." They also chanted "Five, six, seven, eight -- Israel is a terror state," the Times said.
Since Saturday, Israel has been conducting missile strikes into Gaza. At least 300 people have died and another 650 people have been injured.
Demonstrators blocked the streets near the embassy, bringing traffic to a standstill.
The demonstration in London was one of many anti-Israel protests worldwide, with large protests reported in Paris, Madrid and Amman, Jordan.