BBC news with Nick Kelly.

There have been heated exchanges during the latest televised debate between the main US Republican presidential hopefuls. It was dominated by attacks on the front runner Donald Trump by his two biggest rivals. Senator Ted Cruz questioned Mr. Trump's rhetoric. “I understand the folks who're supporting Donald right now. You're angry. You're angry at Washington and uses angry rhetoric. But for forty years, Donald has been part of the corruption in Washington that you're angry about.” He also said Mr. Trump had a patchy record of support for previous Republican presidents. This was Donald Trump's response. “I support politicians. In 2008, I supported Hillary Clinton. I supported many other people by the way. And that was because of the fact that I'm in business. I did support very heavily Ronald Reagan. I also supported George Bush by the way.”Senator Marco Rubio questioned whether voters could trust what the tycoon said. Mr. Trump retorted by accusing Mr. Rubio of letting the electorate down by not voting enough in the senate.

The North Korean leader Kim Jong-un has ordered his military to be ready to fire the country's nuclear weapons at a moment's notice. Mr. Kim's remarks followed new United Nations' sanctions in response to a nuclear test and rocket launch in January.

Some of America's biggest technology companies have made a legal intervention in support of Apple in its dispute with the FBI and the US Justice Department. Apple is refusing to comply with the court order that requires the company to develop new software. This will enable the FBI to access encrypted data on the iPhone that belonged to Syed Farook who with his wife killed 14 people in California. Here's Dave Lee. They may be fierce rivals online and in stores. But in court, it's a powerful alliance. Amazon, Google, Facebook, Intel,Twitter, Snapchat, Microsoft, just about every huge name in technology you can think of, has formally pledged its supports for Apple. They're joined by dozens of law professors and privacy rights groups and their view is clear. They feel the FBI's request to weaken an iPhone's encryption would be a disaster for online security.

The Brazilian Supreme Court says the speaker of the Lower House of congress Eduardo Cunha must face corruption charges. The move could weaken efforts to impeach President Dilma Rousseff. Mr. Cunha has been leading those efforts. He's accused of taking five million dollars in bribes, a charge he denies.

Scientists in Britain say they have discovered a potential weakness inherent in all cancer cells that could pave the way to personalize treatment even in advanced stages. Researchers found that the earliest mutations of cancer are displayed on every cell in a tumor. The ground-breaking discovery should allow them to use the T-cells of the body's immune system to recognize and attack cancer wherever it shows up.

World news from the BBC.

Almost two weeks after cyclone Winston devastated parts of Fiji, aid agencies have called for international relief efforts to be stepped up to help islanders in urgent need of food, water and shelter. Entire villages have been destroyed and it is estimated that half of all homes across the Pacific Island nation will need to be rebuilt.

Scientists in America say a vaccine for the zika virus could be ready for human trials by August or September. The research is taking place at the National Institute of Allergy and Infectious Disease in Maryland. Tulip Mazumdar is there. The scientists in this lab helped to develop an advanced vaccine for Ebola. Now they are trying to do the same for zika with the special focus on pregnant women because of the strongly suspected link between the virus and babies being born with underdeveloped brains. Doctor Anthony Fauci,the institute's director says he's hoping human trials will start in America soon. 'We will have vaccine that's ready to go into humans to test towards the end of this summer or early fall'. These phrase one trials are only the start of a long process. The earliest scientists here expect to have vaccine is 2018.

Allegations of sexual exploitation or sexual abuse by UN peacekeepers have increased according to a new report. There were 69 claims last year compare with 52 in 2014. They're alleged to involve military personnel, international police,other staff at 10 missions. Almost 1/3 of the claims in 2015 were made in the Central African Republic.

And the Japanese Prime Minister Shinzo Abe has agreed to suspend the land reclamation work needed for the relocation of controversial US military base on Okinawa Island in line to the court order. Mr. Abe said the central government would try to reach an amicable settlement with the administration in Okinawa which wants the Futenma base removed from the island completely. BBC news.