LISBON, Portugal (AP) _ A conservative Christian Democrat and a Socialist took a rest Monday before hitting the campaign trail again for next month's runoff election for the presidency.

Christian Democrat Diogo Freitas do Amaral narrowly missed a first-round victory in Sunday's balloting, capturing 46.31 percent of the vote and running far ahead of his three left-wing rivals.

A majority of 50 percent plus one was needed to avoid a runoff.

Socialist Party leader Mario Soares received 25.43 percent and will face Freitas do Amaral in the Feb. 16 election.

Eliminated were Franciso Salgado Zehna, who left the Socialists last month to accept the backing of outgoing President Antonio Ramalho Eanes; and Maria de Lourdes Pintasilgo, the head of an interim government named by Ramalho Eanes in 1979.

Salgado Zehna won 20.89 percent of the vote and Mrs. Pintasilgo 7.37.

Soares said Monday the results showed ''the left still has a majority in Portugal.

Freitas do Amaral told reporters, ''The second round has now begun.''

Ramalho Eanes, a former army general, was barred by law from seeking a third, five-year term.

Police said shots were fired early Monday outside the Communist Party headquarters in the northern city of Oporto as an estimated 300 youths waving Christian Democratic Party banners demonstrated outside the building.

Police said there were no injuries and the crowd dispersed peacefully when patrols were sent to the scene.

A Communist Party official said the demonstrators shouted ''Death to Communists 3/8'' and ''Communists to Siberia 3/8''

Freitas do Amaral's campaign headquarters issued a statement Monday condemning ''any attitude that disturbs the climate of serenity, tolerance and democratic conviviality''.

Freitas do Amaral had received the backing of Prime Minister Anibal Cavaco Silva's centrist Social Democrats who formed a minority government following the Parliamentary elections on Oct. 6.

There have been 16 governments since a coup by leftist military officers in 1974 ended a half a century of right-wing dictatorships.