
Inter have 68 points with nine Serie A games left ahead of a home game Saturday with third-placed Juventus.
Inter started well at the Luigi Ferraris with Zlatan Ibrahimovic firing high before squaring on 11 minutes a low cross for an easy flick home from Honduras' David Suazo.
Controlling the game was easy for Inter only until the 40th minute, when they lost the young Portuguese Pele to a second second yellow card.
Marco Borriello came on for Genoa after the break and aimed a high header followed by a feeble one on 62 minutes before levelling with five to go.
The young striker, who now leads the scorers' table on 17 goals, volleyed home a spectacular overhead kick after Brazilian goalkeeper Julio Cesar managed to save a fast drive from Croat Ivan Juric.
The Rome derby saw an early pressing from Lazio hold Roma in their midfield, and on seven minutes Alexander Doni had to slap against bar a free kick from Aleksandar Kolarov.
Luck, however, lent Roma a big hand on 31 minutes when an unvoluntary deflection from Brazilian Rodrigo Taddei stunned Marco Ballotta.
The goalkeeper stood no chance when a clearance from Swiss defender Valon Behrami bounced off the Brazilian's chest to the net behind him.
Lazio did not relent and levelled before the break through a close-range flick from Macedonian Goran Pandev. Another chance went begging for Lazio on 55 minutes as Serbian free-kick Alexandar Kolarov grazed the post to left of Doni.
A spot kick on 57 minutes allowed Tommaso Rocchi to put Lazio in the lead as Brazil defender Juan floored Rolando Bianchi, but Simone Perrotta equalized for Roma four minutes later with a precise low shot.
Fast and frequent reversals inflamed the Stadio Olimpico until Behrami sealed Lazio's win in stoppage time firing home from a few metres off.
A lacklustre Juventus drew 0-0 at lowly Empoli as a brace from Argentinian Ezequiel Lavezzi sank fourth-place Fiorentina in a 2-0 defeat. AC Milan also lost 2-1 at home to Sampdoria, remaining four points behind the last available Champions League berth.
Udinese won 1-0 at Torino, lowly Parma beat Palermo 2-1 through an Igor Budan brace in a game that both sides ended with 10 men.
Bottom side Cagliari won 1-0 over 10-man Atalanta, Catania and Siena drew 0-0, and Livorno played out a 1-1 draw with Reggina, who lie second-last with Empoli.
By Alberto Cagliano, dpa