Sharif and Hanif are alleged to have carried out the attack
Two Britons accused of a Tel Aviv suicide bombing were allegedly seen visiting a Gaza apartment belonging to a pro-Palestinian group five days before the attack.
Raphael Cohen, an activist for the International Solidarity Movement (ISM), which carries out what it call 'non-violent direct action' against Israeli occupation of Gaza and the West Bank, said he spoke to the pair on 25 April for about 15 minutes.
He said they told him they were not attached to any particular organisation.
Last week's blast at a bar called Mike's Place claimed the lives of three people and injured 55.
The Israeli security services said the attack was carried out by Asif Muhammad Hanif, 21, from Hounslow, west London, and Omar Khan Sharif, 27, from Derby.
Mr Hanif died in the explosion, while Mr Sharif is being hunted by Israeli police, who say he fled the seafront bar after the bomb he was carrying failed to go off.
The attack is thought to be the first by foreign sympathisers since the start of the current uprising in 2000.
Israeli police had said they thought the two men arrived from Gaza a short time before the attack.
Mr Cohen confirmed he met the men, who were given a cup of tea at the ISM office.
He told the BBC's Nick Thorpe in Tel Aviv: "I did meet them, I did say 'Who are you? What organisation do you belong to?
"They said they did not belong to any organisation, but I did not form any impression of them."
After a 15 minute chat, the three men joined a group of 20 people to lay flowers at a nearby site where an activist was killed, before they went their separate ways.
Despite increasing pressure from Israel, the ISM has pledged to continue its work, which it describes as non-violent resistance to the Israeli occupation of Palestinian land.
ISM organises demonstrations against Israeli army demolitions of targeted Palestinian homes.
On 16 March ISM activist Rachel Corrie, a 23-year-old American, was killed by an Israeli bulldozer.
Another ISM volunteer, Briton Tom Hurndall, 22, is still in a coma in an Israeli hospital after being hit by gunfire.
The army's chief of staff has said the movement will be expelled for getting in the way of his soldiers.
In the UK, anti-terrorist police are continuing to question six people in connection with the attack in Tel Aviv.
The British investigation involves MI5, MI6, Scotland Yard's anti-terrorism branch, local police forces and international agencies.
Chancellor Gordon Brown has ordered the freezing of all UK accounts owned by Mr Sharif and Mr Hanif.