Gasoline prices continue to rise in the Washington area and nationally yesterday as Gulf announced a 5-cent-a-gallon increase. The announcement follows by a day 6-cent-a-gallon price incease by Exxon.

Dealers are expected to pass the increase through to customers during the next few days. Gulf controls about 13 percent of the gasoline market here and Exxon 24 percent.

Amoco, with 26 percent of the Washington market, announced a 2-cent-a-gallon increase here last Saturday.

Most Gulf dealers here were already charging well over $1 a gallon before yesterday's announced increase.

All these increases were announced prior to any price increase decision by the Orgaanization of Petroleum Exporting Countries, currently meeting in Caracas.

More increases at the pump will result from any OPEC decision to increase prices. Spokesmen for Gulf, Exxon and Amoco said their increases in the last few days were not made in anticipation of any OPEC action but were based on past costs of obtaining crude oil.

Exxon's increase was caused partly by a decision last week by Saudi Arabia to raise its crude oil prices $6 a barrel, a "moderate" political political move viewed as an effort to encourage other OPEC members to limit their increases.

Supplies of gasoline here and nationally continue to be tight but adequate, spokesman said.