The US has given Russia information American subs picked up when the submarine Kursk went down. Two US nuclear subs were using their sensors to monitor the Russian exercise when, at 11:28 AM (local time) on August 12, they detected two underwater explosions. The second one came two minutes after the first one and appeared to involved one to five tons of explosives. It was some 50 times larger than the first blast. Chechnya was locked down by military patrols and a massive show of force by the Russians to prevent any rebel celebrations of this, their self-declared independence day. There were several rebel attacks anyway and several Russian soldiers were killed.