Iran warned it could be pushed into building a nuclear weapon if Israel continues to threaten its existence, in an unusually frank admission by a senior official. "We have no decision to build a nuclear bomb but should Iran's existence be threatened, there will be no choice but to change our military doctrine," said Kamal Kharrazi, an adviser to Supreme Leader Ayatollah Ali Khamenei. The comment raised questions afresh about what Iran has long claimed is a peaceful nuclear programme.

Khamenei, who has the final say on the matter, banned the development of nuclear weapons in a fatwa, or religious edict, in the early 2000s, saying it is "haram", or forbidden in Islam. Despite that, Western governments throughout the 2000s and 2010s till today have adopted a working assumption that Tehran is working towards a nuclear capability. Iran is enriching uranium to up to 60 percent purity, whereas weapons-grade uranium is enriched to about 90 percent.

Pakistan's military said a suicide bombing that killed five Chinese engineers and a Pakistani driver in March was planned in neighbouring Afghanistan and that the bomber was an Afghan citizen. At a news conference, army spokesman Maj. Gen. Ahmad Sharif said four men behind the March 26 attack in Bisham, a district in Khyber Pakhtunkhwa province, had been arrested. The attacks have prompted several foreign embassies to take extra security measures.

Sharif said the attack that killed the Chinese engineers, who were working on Pakistan's biggest Dasu Dam, was an attempt to harm the friendship between Pakistan and China. Thousands of Chinese are working on projects relating to the China-Pakistan Economic Corridor. Sharif also said Pakistani Taliban who have sanctuaries in Afghanistan were behind a surge in attacks inside Pakistan since January that killed 62 security forces nationwide, and that Pakistan had solid evidence of the group's involvement in the rising violence.

The death toll from unseasonable flooding in southern Brazil reached 100, the local civil defence agency said, as emergency crews continued to search for dozens of missing people. Nearly 400 municipalities were affected after days of heavy rains that swamped the state of Rio Grande do Sul. The floodwaters injured hundreds of people and forced 160,000 others from their homes as of Wednesday, while the state civil defence authority said 128 people were still missing.

Brazil's national centre for natural disasters said the southern part of the state was under "high risk" of more floods throughout the day. It said rainfall was expected to restart, and although it was not expected to be significant in volume terms, water levels are already high in many places and the soil is saturated. Many residents have no access to drinking water or electricity - or even the means to call for help with telephone and internet services down in many places.

After more than three billion doses, the Oxford-AstraZeneca Covid vaccine is being withdrawn. AstraZeneca said it was "incredibly proud" of the vaccine, but it had made a commercial decision. It said the rise of new coronavirus variants meant demand had shifted to the newer updated vaccines. Its vaccine was estimated to have saved millions of lives during the pandemic, but also caused rare, and sometimes fatal, blood clots.

In the race to lift the world out of pandemic lockdowns, the Covid vaccine was developed by scientists at the University of Oxford in record time. A process that normally takes 10 years was accelerated down to about 10 months. In November 2020, it was heralded as "a vaccine for the world" as it was far cheaper and easier to store than other Covid vaccines. The pharmaceutical giant AstraZeneca had agreed to manufacture it en masse.