(Updates toll)

SANAA, Oct 13 (Reuters) - Four people were killed and at least four others wounded on Saturday when unidentified gunmen opened fire on opposition activists planning a rally, police said.

Earlier, opposition sources said Yemeni security forces had clashed with activists in the southwestern province of Lahij because the activists did not have government permission to stage a rally.

Police said they were trying to track down the gunmen.

Yemeni authorities issued a ban in August on people holding demonstrations without permission after opposition parties staged several protests demanding the government take steps to curb inflation in one of the poorest countries outside Africa.

There have been a number of clashes between Yemeni police or armed forces and protesters in recent months, some ending in fatalities.

Two people were killed and 10 wounded on Sept. 2 during a demonstration against rising prices of basic goods. Two others were killed on Sept. 10 during a protest to demand the release of people held during earlier price riots.

Saturday's clash was not related to prices. Opposition parties were planning a rally to mark the anniversary of the Oct. 14, 1967, uprising against British occupation.

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