Hammarby were within touching distance of Sirius before taking one point from their previous two games, but looked to be getting themselves back on track just eight minutes in when Victor Lind fired in a low cross which Paulos Abraham did well to control before bundling in from six yards.
But with three wins in their previous four, Brommapojkarna were a force to be reckoned with, as they proved before the half-hour mark when Oliver Zanden got free down the left and cut the ball back for Mads Hansen to sweep into the net.
However, Bajen found a crucial second goal in first-half stoppage time - following patient build-up, the home side switched play to Montader Madjed on the right, and his low centre was struck low and true by Markus Karlsson.
That goal gave the hosts a platform to build on in the second half, and they did just that a little over 10 minutes after the restart - Lind grabbed his second assist of the game with a free-kick from out wide on the left, which was flicked goalwards by Frederik Winther.
Hammarby move to 40 points, five behind Sirius ahead of the Uppsala side playing Degerfors on Monday 14th. BP sit 11th, eight points clear of the bottom three.
Malmo moved up to fifth in the table after turning a tight game at home to Orgryte into a rout, extending their unbeaten run to three games, while OIS are six without a league win and still four points from safety.
There was bad news for MFF in the first half as youngster Kenan Busuladzic went down off the ball and appeared to suffer a bad knee injury. The game was still goalless until just before the hour mark, when Theodor Lundbergh turned his marker, drew the goalkeeper and squared for Jovan Milosavljevic - Busuladzic's replacement - to tap in on his first Allsvenskan appearance.
It was 2-0 with just under 20 minutes to play, as Malmo won the ball back high up the pitch, and after Daniel Tristan Gudjohnsen had one shot blocked and another saved, Otto Rosengren followed up to head in the second rebound.
A foul by Stian Gregersen inside the area 10 minutes later allowed Tobias Sana to strike Orgryte back into the match from the penalty spot, only for Rosengren to have another say in the 90th minute, teeing up Bleon Kurtulus to restore the home side's two-goal advantage.
Another difficult afternoon for OIS was compounded in added time when Owen Parker-Price turned the ball into his own net, as Malmo moved within five points of the European places.
Kalmar remained hovering above the relegation zone on goal difference and Elfsborg climbed to fourth, four points off the European places as the home side took a narrow victory in Boras.
The only goal of the game arrived six minutes into the second half, when a neatly-timed pass from Leon Ostman sent Momoh Kamara through on goal, and he kept his composure to clip the ball coolly past the goalkeeper.
KFF had chances to draw level, but for the fifth league game in a row, they drew a blank in front of goal and are now six without an Allsvenskan victory. Elfsborg have now won three in a row at home without conceding.
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