LOS ANGELES — Tom Brady and the New England Patriots slid to a second straight defeat on Sunday, falling 23-16 to the Kansas City Chiefs in a game marred by a series of officiating blunders.

The reigning Super Bowl champions launched a spirited fightback after trailing 23-7 in the third quarter but lost crucial momentum after multiple calls went against them at Foxborough.

The most glaring officiating error occurred early in the fourth quarter, when N'Keal Harry was wrongly adjudged to have been forced out of bounds as he dived into the corner for a touchdown.

Replays clearly showed Harry was in-bounds and the Patriots should have been awarded a touchdown – but with coach Bill Belichick already out of challenges, the call was allowed to stand.

With the drive eventually ending in a Patriots field goal, the hosts turned around 23-16 instead of potentially cutting the Chiefs lead to 23-20 with most of the fourth quarter remaining.

The officiating crew had also blown an earlier call, mistakenly whistling play dead after failing to spot a Travis Kelce fumble, denying the Patriots a potential defensive touchdown.

The Patriots – who had been booed off the field at halftime after trailing 20-7 – had one last attempt for a game-tying score, but Brady's pass to Julian Edelman in the endzone was batted away by Bashaud Breeland.

Patriots coach Belichick refused to be drawn on the officiating performance following the loss.

Asked what officials had said after disallowing Harry's touchdown, Belichick replied: "You'll have to talk to them about that. I'm not going to speak for them."

"I was proud of the way our guys competed tonight," he added. "They battled for 60 minutes. Wasn't always perfect, and there's certainly things we could have done better. But we were competitive right the way down to the final play."

Asked about the boos his team had been subjected to at half-time, Belichick added: "We're just trying to win games."

The Patriots fell to 10-3 with the loss but lead the AFC East.

The Chiefs, meanwhile, clinched the AFC West divisional title with the win, improving to 9-4.

Elsewhere Sunday, the New Orleans Saints also clinched their division despite losing a thriller against the San Francisco 49ers, going down 48-46 in the Superdome.

Niners quarterback Jimmy Garoppolo finished with 349 passing yards from 26 completions as San Francisco rallied superbly with a late drive after Drew Brees had helped the Saints take a 46-45 lead with less than a minute left.

Garoppolo showed great composure as the seconds ticked down, converting a do-or-die 4th & 2 with a short pass to find tight end George Kittle.

Kittle then charged forward, shrugging off the attentions of two tacklers to advance 39 yards and take the 49ers within field goal range.

It was left to veteran kicker Robbie Gould to deliver the decisive field goal, the 37-year-old nailing his kick from 30 yards to silence the Superdome in dramatic fashion.

The win sees the 49ers improve to 11-2 to regain first place in the NFC West division, although Seattle would reclaim top spot with victory over the Los Angeles Rams later Sunday.

The Saints meanwhile fell to 10-3 with the defeat, potentially complicating their route through the playoffs as they chase a berth in the Super Bowl in Miami in February.

In other games on Sunday, the Baltimore Ravens sealed their playoff berth with a 24-17 defeat of the Bills in Buffalo.

Ravens quarterback Lamar Jackson threw three touchdowns but ended with only 145 yards and 16 completions on a day when neither offense managed to fire on all cylinders.

The Ravens now lead the AFC North on 11-2.

At Lambeau Field, Aaron Rodgers threw for 195 yards and a touchdown as the Green Bay Packers defeated the Washington Redskins 20-15.

The Packers improved to 10-3 with the win to tighten their grip on the NFC North. — AFP