Labour Party European election candidate Del Singh and security worker Simon Chase were killed late on Friday night when two Taliban members stormed the Taverna du Liban and opened fire on diners after detonating a bomb outside.
Among those killed in the attack, which occurred deep in the city's diplomatic enclave, were two US nationals, one Russian UN official, a Canadian, a Dane, a Lebanese representative of the International Monetary Fund, and eight Afghanis.
Labour leader Ed Miliband paid tribute to Del Singh and described the attack as a "barbarous act of terror".
The blast at the restaurant represents a strike at the heart of the international diplomatic community in Afghanistan in one of the areas which would previously have been considered safe.
The suicide attacker detonated his explosives outside the gate of the heavily fortified building, before the two gunmen entered the restaurant and started shooting at people inside. It is believed they were shot dead by security forces when they arrived at the scene.
The restaurant is in an area that is home to several embassies, non-governmental organisations and the homes and offices of Afghan officials, and like most places frequented by foreign diplomats, aid workers, journalists and businessmen, has no signs indicating its location and is heavily secured.
It is on a small side street in the diplomatic quarter of the central Wazir Akbar Khan area, in a house with low ceilings and an enclosed patio, but no windows.
Simon Chase, a former British soldier, was originally from Merseyside but had been living in Limavady in Northern Ireland with his fiancee Norma McDowell. The healthcare worker was being comforted yesterday by family and friends. It is understood the couple lived together with two children.
The ex-Cheshire Regiment soldier worked in Kabul in the security industry.
Mayor of Limavady Gerry Mullan extended his condolences.
"There is a cloud that has descended upon the local community who are very shocked and saddened by his loss," said the SDLP councillor. "He was a well-known and well-respected figure in the community."
Del Singh had previously worked on development projects in Afghanistan, Kosovo, Sudan, Sierra Leone and other countries.
Miliband said: "My thoughts - and the thoughts of the whole Labour Party - are with the family and friends of Del Singh who was killed in yesterday's tragic suicide bomb in Kabul.
"People everywhere will be appalled and shocked by this barbarous act of terror deliberately targeting members of the international community."
The International Monetary Fund's (IMF) representative in Afghanistan, 60-year-old Lebanese national Wabel Abdallah, was one of the other diners killed. He had been leading the office in Kabul since 2008.
The three UN staff included a Russian, an American and a Pakistani. The Russian was the senior UN political officer trying to negotiate a start to peace talks with the Taliban. UN spokesman Ari Gaitanis said: "You can imagine the effect it has had on staff members here."