BBC news with Iain Purdon.

An explosion at a petrochemical plant in southeastern Mexico has killed 3 people and injured more than 1030. The plant is a part owned by Mexico's state oil company Pemex. Here is Nicolas Russia.

Officials at Pemex say they're investigating the cause of the blast in the port city of Coatzacoalcos. The explosion sent dark plumes of smoke over the city, forcing the evacuation of schools and businesses. The Veracruz state governor Javier Duarte recommended that people stay indoors even though the fire has been brought under control and the cloud of toxic smoke is dissipating. In February, 2 people were killed and at least 7 injured in a Pemex oil platform off the coast of Campeche, also in the southeastern Mexico.

The United Nations says an operation is underway to evacuate hundreds of wounded or sick people and their families from 4 besieged Syrian towns. Two of the towns are being blockaded by pro-government forces. The other two are surrounded by Islamist rebel groups. Here is Daniel Bard.

The complex operation supervised by the Syrian Red Crescent began on Wednesday. Each of it sees 250 people evacuated from the mainly Shia pro-government towns of Alfua and Kefaria in Idlib province and a similar number evacuated from the rebel-held towns of Sadani and Madaya near Lebanese border. The United Nations spokesman Stéphane Dujarric said some of those evacuated on Wednesday needed urgent medical attention. It's a small sign of progress on the humanitarian front, an issue that's bedeviled faltering peace talks in Geneva.

The government of El Salvador says it's deploying a new heavy-armed unit to fight the country's notorious criminal gangs which has started operating in rural areas. The special force of 1000 soldiers and police will operate with helicopters, armored cars and assault weapons. The minister of defense said they would target about 100 gang leaders who'd left the cities because of government raids. El Salvador has one of the highest murder rates in the world largely due to turf wars between the country's gangs.

The Canadian government is to make good on one of the prime minister Justin Trudeau's campaign pledges and introduce legislation that could lead to the legalization of marijuana. Laura Bicker reports.

The prime minister Justin Trudeau argued for the drug to be legalized during his election campaign. His health minister says she wants to keep it out of the hands of children and profits out of the hands of criminals. The government has pledged to work with police to control who is sold to, when it's sold and how it's used and it compared with to regulate the drug to alcohol laws. However, opposing conservatives say one of the worst things for young people in Canada would be to open the door to marijuana use.

World news from the BBC.

Reports suggest that Volkswagen and American officials have reached a deal under which the carmaker could offer to buy back up to half a million cars in the US that exceed illegal emission levels. The carmaker could also set up a compensation fund of more than 1 billion dollars for owners. VW is expected to give more details of the deal to a federal judge later today.

Australia is hoping to boost its defense against online attacks with the launch of 220 million dollar initiative. The Australian authorities have also acknowledged for the first time that the country can respond to cyber threats by launching attacks of its own. From Sydney, Phil Mercer.

Last year, China was suspected of infiltrating Australia's Bureau of Meteorology that affected its entire computer network. The government in Canberra won't comment on the security breach but it's responding to the ever present threat of cyber crime. The prime minister Malcolm Turnbull said Australia is to boost its online defenses. There'll be closer collaboration between the government and businesses and a special ambassador will be appointed.

Queen Elizabeth is celebrating her 90th birthday today. She'll meet members of the public during a walkabout with the Duke of Edinburgh in Windsor. Later, Britain's longest reigning monarch will light the first in a chain of about 1000 beacons. They'll be lit across the UK and other countries.

The education authorities here in England have been left with red faces after it emerged that a spelling test due to be taken by half a million 7-year-olds was published online as a sample paper a few months ago. The mistake was discovered when a school running an official trail of the new national spelling test noticed that some of the pupils recognized the words. The tests have already been distributed to schools to be used during the first week of May.

BBC news.