For the first time in seven months, a Soviet spy ship has been sighted off the coast of Israel in the Mediterranean sea, Israeli military sources confirmed today.

The vessel, disguised as a fishing trawler named Lomar, is said to carry highly sophisticated electronic eavesdropping equipment and a team of communications experts to monitor all radio-telephone traffic along the Mediterranean coast and inland throughout the Middle East, especially U.S. military and intelligence communications.

The ship, sighted about 15 miles off the coast of Israel, used to be a permanent fixture in the region, but Israeli officials said it disappeared about seven months ago. Its regular port of call is Latakia, Syria, which is the principal port for Soviet arms shipments to Syria.

Officials said the return of the Lomar to the Mediterranean probably was prompted by reports that the United States is considering increasing its military presence in Israel, Egypt or both and by developments in Iran and Afghanistan.

Meanwhile, growing Soviet influence in the Middle East and central and eastern Asia is expected to be a principal topic on the agenda of a summit between Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin, beginning Monday in Aswan.

A source close to Begin said regional strategic discussions probably will eclipse the scheduled talks on the normalization of relations between the two countries and discussions on proposed automony for 1.1 million Palestinian Arabs in the occupied West Bank and Gaza Strip.

Begin's itinerary in upper Egypt includes ancient sites in Aswan, Luxor and Abu-Simbel, near the Sudanese border.