Residents said between 200 and 300 people took part in the march in Saudi Arabia’s oil-producing Eastern Province.
Many protesters held pictures of Palestinians wounded in Israel’s military offensive against the Gaza Strip, which has killed more than 300 Palestinians since it began on Saturday.
At least three witnesses said they saw riot police fire rubber bullets after demonstrators clashed with security forces in the al-Qatif area.
However, Interior Ministry spokesman Mansour al-Turki said there had been no protest.
"None of this is true. No rubber bullets have been fired, no clashes occurred and no demonstration happened. That’s what security sources in Qatif told me," he said.
"As you know, protests in the kingdom are banned."
One witness said two demonstrators were injured by rubber bullets. Two others said between six and eight were injured.
"We chanted slogans against Israel and America. We did not attack the (Saudi) government or the Arab political system," said another witness, who did not want to be named.
"The police charged at us with sticks and electric batons. Some of us had to defend ourselves with shoes and rocks."
One resident said the police had dispersed the crowds and blocked the main street in al-Qatif.
