A rally has been held to show support for people in northern Israel caught up in the crisis in the Middle East.
Foreign Office minister Kim Howells has criticised Israel
Israel's ambassador to the UK, Zvi Heifetz, told the event in Kenton, north-west London, that "Israel has the right to defend its people".
Organisers, the Board of Deputies of British Jews, said about 7,500 attended. A police officer put the figure at between 4,000 and 5,000.
Thousands have attended UK protests against Israel's attacks on Lebanon.
Henry Grunwald QC, president of the Board of Deputies of British Jews, opened the speeches at Sunday's event at a school in Kenton.
He said: "Of course we express and show sadness for the loss of innocent lives on all sides but we're here to send a strong message of support to the people of Israel."
Mr Heifetz said that recent international meetings such as the G8 summit had shown that Israel was "not alone".
"The leaders of the civilised world are not blind to the facts. Their message was clear - Hezbollah is responsible. And Israel has the right to defend its people," he said.
The rally, lasting more than an hour, featured singing, chanting and Jewish prayers, and a live video link to a bomb shelter in northern Israel.
Avi Krampa, an Israel mayor who spoke over the link, said: "I want you to know that our people are strong, they are brave and they are not giving up."
Men, women and children attended the rally, with many people holding placards that read: "Yes to peace, no to terror."
A small counter-demonstration was staged outside the event by Jewish people opposed to military action in Lebanon.
'Crimes against humanity'
On Saturday, 11 rallies against Israeli attacks were organised by groups such as Stop The War Coalition and the Muslim Association of Britain.
They were held in Birmingham, Glasgow, Kirkcaldy, London, Manchester, Newcastle, Sheffield, Edinburgh, Exeter, Norwich and York.
Police estimated that 7,000 people took part in the London rally but organisers said more than 20,000 people had attended the march from Whitehall to Hyde Park.
The protest in London was one of many in the UK on Saturday
The Palestine Solidarity Campaign, British Muslim Initiative and Lebanese organisations were also involved in organising demonstrations against what they call Israel's "crimes against humanity".
A spokesman for the protests said: "Israel's war in Gaza and Lebanon is escalating into an international crisis which could soon engulf the whole region.
"The promise by Bush and Blair, in the lead up to the Iraq war, that their wars would bring freedom and democracy to the Middle East and peace to Palestine have yet again been shown to be lies, just as the anti-war movement has consistently said they were."
Israel says its attacks on targets in Lebanon are aimed at securing the release of two Israeli soldiers, who were captured by Hezbollah militants on 12 July, and preventing further Hezbollah rocket attacks on northern parts of the country.
Thousands of civilians are struggling to leave southern Lebanon, as Israel continues air strikes and ground raids.
The UK evacuation of British nationals from Lebanon to Cyprus has now been completed, with about 4,000 people having left the country.