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KNOW IT ALL: Thursday's Top 6 Stories at NBC News

From fatal clashes in Ukraine to the ongoing search for survivors of the sunken South Korean ship, see the stories we're following.

Good morning, and happy Thursday. Here are some of the stories we're following today:

1. Ukrainian security kills 3 pro-Russian separatists at port base

The protesters were hurling Molotov cocktails and opened fire on Ukrainian personnel during Wednesday’s skirmish near a military base in Mariupol, local reports said. Three of the pro-Russian separatists were fatally shot as about 300 of them reportedly tried to seize the base. Secretary of State John Kerry is expected to meet with Russian, Ukrainian and European leaders today to talk about the ongoing crisis. Read more in NEWS.

Russian President Vladimir Putin, meanwhile, has denied that Russian forces have crossed into eastern Ukraine.

2. Treacherous conditions thwart rescue effort of sunken ship

The death toll has risen to at least nine after a ship carrying mostly high school students capsized off the coast of South Korea on Wednesday. Nearly 300 people remain unaccounted for, and efforts to rescue them were difficult today because of strong currents. Desperate families have hired their own boats to try and get close to the ship. Read more in NEWS.

3. Sub searching for missing jet completes first ‘full mission’

The unmanned submarine, Bluefin-21, began scouring the Indian Ocean for the vanished Malaysian airliner earlier this week, but had a couple of technical setbacks. So far, it has searched about 35 square miles of a 230-square-mile patch off the coast of Australia. Officials remain hopeful the sub can find the jet, but its initial search yielded “no significant detections.” An oil slick in the area was also analyzed and determined not to have come from the missing plane. Read more in NEWS.

4. Militants free most of abducted Nigerian schoolgirls

Islamist Boko Haram militants are accused of kidnapping more than 100 teenage girls from their school in Borno on Monday. While most of the hostages were set free, at least eight remain missing, military officials said Wednesday. The mass abduction has shocked Nigeria, where Boko Haram fighters have brought lawlessness to parts of the country. Read more in NEWS.

5. ‘X-Men’ director accused of drugging, raping teen

Producer and director Bryan Singer, 48, is accused of sexually abusing a teenage boy in the late 1990s, according to a lawsuit filed Wednesday. The plaintiff, now in his 30s, is expected to appear at a news conference today in Los Angeles. The suit claims Singer and other Hollywood insiders threatened to “destroy his hopes and dreams of an acting career if he did not keep them happy.” Singer, whose new “X-Men” movie hits theaters next month, did not immediately respond. Read more in POP CULTURE.

6. Fired Yahoo exec received $58M golden parachute

After 15 months as chief operating officer, Henrique de Castro left the Internet giant with a $58 million severance package, it was revealed Wednesday. Yahoo CEO Marissa Mayer axed de Castro in January after he failed to grow the company’s ad sales. It was a costly mistake, and Mayer says she won’t replace him. Read more in BUSINESS.

… What’s trending today?

This is how NOT to take a selfie.

A YouTube user trying to take a picture by a moving train was suddenly whacked in the face — by the conductor’s foot.

“I tried to take a selfie while a train passed a ‘safe’ distance behind. I guess I was still too close and got kicked in the head,” the user wrote. “I messed up.”