Roberto Mancini was making his return as Inter coach after six years away from the San Siro, but could only watch on as his side fell behind to a Jeremy Menez goal after 23 minutes.
However, Inter rallied after the interval and Obi’s strike in the 61st minute earned Mancini’s men a point which keeps them within touching distance of their seventh-placed rivals.
Cagliari twice came from behind to register an impressive 3-3 draw against third-placed Napoli in what was a thrilling end-to-end encounter at the San Paolo.
Napoli went two goals up through Gonzalo Higuain and a terrific long range Gokhan Inler effort before Cagliari levelled either side of the break, through Victor Ibarbo and then Diego Farias.
Jonathan de Guzman gave Napoli the lead once again before Farias brought his side back level for a share of the points.
An own goal by substitute Constantin Nica handed Sampdoria a 1-1 draw at Cesena.
The hosts were on course for their first win since August 31 after Stefano Lucchini scored on the hour against his former club, but with 13 minutes remaining Nica deflected Citadin Eder’s cross into his own net to pull Samp level.
Udinese captain Antonio Di Natale scored his 200th Serie A goal but the Friuli outfit had to settle for a point at home to Chievo after playing out a 1-1 draw.
Searching for their first win in four games, the hosts went ahead when Di Natale scored on the stroke of half-time.
Ivan Radovanovic then equalised for Chievo in the 74th minute with a stinging drive from 25 yards which beat Udinese goalkeeper Orestis Karnezis.
Empoli clinched their first away win of the season with a 2-0 success at Parma to pile more misery on the foot-of-the-table Gialloblu.
The Tuscan outfit went ahead with Matias Vecino’s strike on the stroke of half-time and he set up Francesco Tavano to double the advantage after the restart.
Substitute Antonio Floro Flores scored three minutes from time to hand Sassuolo a 1-0 victory at Torino which extended their unbeaten run to six games.
Sassuolo goalkeeper Andrea Consigli had earlier saved a penalty from Juan Sanchez Mino.
Fiorentina halted a two-game losing streak with a 2-1 triumph at Hellas Verona.
Nico Lopez cancelled out Gonzalo Rodriguez’s opener for the Viola in the 39th minute before Juan Guillermo Cuadrado fired home the winner in the 62nd minute.