A gunman shot and seriously wounded a Massachusetts Institute of Technology police officer in an eruption of gunfire at the prestigious university late Thursday.
A letter addressed to President Barack Obama tested positive for ricin, and authorities arrested a suspect, stoking alarm in Washington on Wednesday after an earlier scare over poisoned mail.
More Guantanamo detainees have joined a growing hunger strike at the reviled US military prison, with nearly a third of the 166 war-on-terror suspects participating.
A US man whose estranged wife cut off his penis accused her Wednesday of effectively murdering him, recounting his horror as she severed the organ and threw it into a garbage disposal machine.
Bristling with anger, President Barack Obama branded Wednesday's defeat of his gun reform drive in the US Senate as "shameful," and accused lawmakers of caving in to the powerful firearms lobby.
Some 60 to 70 people were killed and hundreds were injured by an explosion at a fertilizer plant outside Waco, Texas, local media reported, citing the local emergency manager.
North Korea laid down rigid pre-conditions Thursday for any talks with Seoul or Washington, including the withdrawal of UN sanctions and a guaranteed end to South Korea-US joint military drills.
Top-flight sport made an emotional return to Boston on Wednesday as the NHL's Bruins paid tribute to the heroes and victims of the twin bombing that killed three in the US city.
The deadly explosives detonated at the Boston Marathon were homemade devices full of nails and metal fragments, possibly packed into kitchen pressure cookers.
The Pentagon has requested $220.3 million in 2014 to bolster Israel's "Iron Dome" missile defense system despite broader cuts to US military spending, according to budget documents.
Orbital Sciences, one of two private US firms chosen by NASA to shuttle cargo to the International Space Station, is preparing for the first launch of its Antares rocket Wednesday.
US hospitals face a disincentive to improve care because they make drastically more money when surgery goes wrong than when a patient is discharged with no complications.
US Muslims are watching closely as the probe into the Boston bombings unfolds, fearing a backlash like after 9/11 if an Islamist link is confirmed to the deadly attack.
Pakistani troops scrambled Wednesday to aid the remote victims of an earthquake centred in nearby Iran, as the United States offered assistance and a strong aftershock jolted the region.