Saudi Arabia's Interior Ministry says five border guards have been killed in an eight-hour-long cross-border clash with militants from Yemen.

The statement, carried on the official Saudi Press Agency, says at around 6 a.m. on Monday border guards repelled attempts by armed groups to cross Saudi Arabia's southern border from Yemen. The Interior Ministry did not identify the attackers, but said the clashes took place in Najran.

A day earlier, the Saudi-led military coalition fighting Yemen's rebel Houthis said the kingdom's air defense forces shot down a ballistic missile fired from Yemen toward Najran. The coalition backs Yemen's internationally recognized government against the Houthis and their allies who control territory inside Yemen.

A cease-fire declared by the U.N. since April 10 remains shaky, with both sides reporting numerous breaches.