Dr Saad al-Faqih, the head of the Movement for Islamic Reform, said that six suspected dissidents were killed in Monday’s exchange of fire in the holy Muslim city.
He described the incident as a “major confrontation in which five security officers were killed and four were wounded including a lieutenant by the name of Nadar al-Maliki”.
His account contradicted an interior ministry official who said that security forces shot and killed two people.
“Saudi authorities were able to prevent a terrorist attack being prepared by terrorists, which did not respect the sanctity of the holy city of Makka and the month of Ramadan,” an interior ministry official was quoted by the state news agency SPA as saying.
In the latest statements, Saudi officials said the plot was aimed at pilgrims.
Saudi authorities surrounded the suspects and opened fire with machine guns and hand grenades. Security sources then responded, said the interior ministry official.
Officials said only one security officer was wounded and the two suspects were killed as they tried to flee in their cars.
Security forces found a cache of arms in the cars including machine guns, pistols, hand grenades, rocket-propelled grenades and barrels with powder used for explosive devices, along with passports and ID cards.
Hunt for suspects
Millions of Muslims will flock to
Makka this month for Umra
They had been hunting a group of six allegedly armed men and located them holed up in a building in the eastern quarter of Makka, said a security source.
Two of the men were killed while four others escaped to the mountains.
But al-Faqih said that only one suspect escaped and that the government “has been anticipating attacks in more than one place in the kingdom and in Makka in particular, to a point that armoured vehicles have been in the streets since the start of Ramadan”.
The dissident attributed the information to sources at the Saudi information ministry.
The kingdom has launched a major crackdown on groups suspected of planning attacks within Saudi Arabia since the 12 May triple bombings of residential compounds in Riyadh that left 35 people killed.
There have since been frequent shootouts in which both security forces and suspects have been wounded or killed. Hundreds of people have been rounded up in security sweeps.