Thousands of Pro-Palestinians March in London

At least 10,000 pro-Palestinian protesters opposed to Israel's military action in Gaza marched through central London for the second week running on Saturday.

A police source estimated the crowds at 10,000, but an Agence France Presse photographer suggested the number could be far higher, forcing the closure of roads around Britain's parliament.

The march started outside the Israeli embassy in Kensington, in the west of the British capital, before passing Downing Street and coming to a halt outside the Houses of Parliament in Westminster.

Demonstrators held placards reading "Stop Israeli State Terror!", "Freedom for Palestine" and "Gaza - End the Siege."

They also chanted "Shame on you David Cameron" as they filed past the British prime minister's Downing Street office.

The crowds took over Parliament Square, where a series of speakers, including Roxy Music member Brian Eno, took to a temporary stage to call for an end to the military campaign, which has claimed more than 1,000 lives, according to official figures.

One speaker urged demonstrators to buy the song "Freedom for Palestine" by One World in the hope that it would enter the top singles chart and receive radio air play.

The event was organized by the Stop the War coalition and Occupy London, among others.

Organizers said that last week's similar protest, which passed off without any violence, attracted 100,000 people, although police put the figure at 15,000.

U.S. Secretary of State John Kerry and top diplomats from Europe and the Middle East meeting in Paris on Saturday called for an extension to a temporary truce currently in force between Israel and Hamas.

Both sides have agreed to a 12-hour "humanitarian" ceasefire in Gaza that started at 0500 GMT Saturday.

New British Foreign Secretary Philip Hammond later insisted there was an "absolute humanitarian necessity" to extend the ceasefire.

The 19-day Israeli offensive on Hamas-ruled Gaza was launched in response to rockets fired by militants of the Islamist group into the Jewish state, and 37 Israeli soldiers have also died in the violence.