MOSCOW (AP) _ A small bomb exploded outside the Moscow headquarters of the influential Russian oil company Sibneft on Thursday. No casualties were reported.

The home-made device, estimated to contain 200 grams of explosives, detonated overnight, police said. It caused a small hole in the sidewalk outside the Sibneft offices across the Moscow River from the Kremlin.

The explosion hit jittery Moscow a week after a bombing ripped through a busy underground passageway at rush hour, killing 12 people and renewing fears of a terrorist bombing campaign.

A Sibneft spokesman said there had been a similar small explosion at the offices a few weeks ago.

Sibneft was investigated by tax police last week in a string of inspections at major oil and gas companies. That raid followed a July spat with the Finance Ministry in which government officials charged Sibneft with paying suspiciously low taxes.

Sibneft, Russia's sixth-biggest oil producer, is bidding with two other companies for an 85 percent stake in Onako, Russia's 11th-biggest oil company. Privatization in Russia has been contentious in the past.