Lazio had won their last four home games but in heavy Rome rain they went down 3-0 to Inter at the Stadio Olimpico.
Mauro Icardi continued his hot streak with a double as Inter cruised to a 3-0 win at a sodden Stadio Olimpico against Lazio in Serie A on Monday.
A sixth straight league win for the Nerazzurri was set up by Icardi's opener, the striker showing his poacher's instinct again after his late header in last weekend's derby victory over AC Milan.
Lazio were also in good form having won three games in a row in all competitions, but when Marcelo Brozovic drilled in a fine second their hopes of a fightback were extinguished in the heavy Rome rain.