BBC News with Nick Kelly

Western leaders have stepped up pressure on Russia to abandon efforts to annex Ukraine's Crimea region or face sanctions. President Obama spoke at the White House after talks with the interim Ukrainian Prime Minister Arseniy Yatsenyuk.

“We will continue to say to the Russian government that if it continues on the path that it is on, then not only us, but the international community, the European Union and others will be forced to apply a cost to Russia's violations of international law.”

Earlier, the European Union and the G7 Group of industrialized nations spoke that they would take action against Russia if the referendum went ahead. The American Secretary of State John Kerry will meet his Russian counterpart Sergei Lavrov in London on Friday to present a series of options for resolving the crisis.

Palestinian militants in the Gaza Strip have fired rockets into southern Israel, the heaviest barrage since 2012. The Israeli military responded with artillery fire into the north and south of Gaza. Quentin Sommerville reports from Jerusalem.

Dozens of rockets could be seen being fired from the southern outskirts of Gaza city according to an eyewitness. In southern Israel, siren sounded and those in range were told to take shelter. One rocket landed near a library, another beside a petrol station. The militant group Islamic Jihad said it carried out the attack in response to an Israeli raid on Tuesday which killed three of its fighters.

The militant group Islamic Jihad said it fired the rockets to avenge the deaths of three of its members killed in an Israeli air strike.

Riot police in Turkey have fired water cannon and teargas at thousands of demonstrators in Istanbul. Mass protests broke out after the funeral of a teenage boy Berkin Elvan who died on Tuesday from injuries caused by a teargas canister during unrest last year. The boy's father Semi told the BBC he wanted his son to be remembered as a child who was killed by the state. But he said he shouldn't be seen as a political symbol, because he wasn't part of any protest, he'd only gone out buy bread. One of the protesters A explained why he was taking part.

“Today we are here to protest the government's, their fascist behavior, actually to mourn the death of a young boy, a younger adult, all his guilt was to buy a lot of bread, and we are here so this doesn't repeat.”

The Chinese authorities have published images of what they suggest maybe three pieces of wreckage from a Malaysian airliner that vanished on Saturday on its way to Beijing. The website of China's State Administration of Science carries three satellite images taken a day after the plane went missing. Coordinates alongside them will place the objects in the South China Sea.

World News from the BBC

Supporters and opponents of the Venezuelan government have filled the streets of Caracas in rival marches, marking one month since the current protests movement began. At least 22 people from both sides of the political divide have been killed in the unrest. One opposition leader Maria Corina Machado told the BBC that most Venezuelans wanted an immediate change of leadership albeit through peaceful means. But a government minister..criticized the opposition's tactics.

“We're seeing a scheme, that we've in the past, it's the effort to destabilize our country, this is a democratic country, we just came out of an election this last December which we won may over 10%, we had four elections in the last two years before that we had presidential elections in April， before that we have Chavez we elected in October. So we've won by an important majority for the last four elections. ”

The mayor of New York Bill de Blasio says an explosion that destroyed two five-storey buildings in the city was caused by a gas leak. Two women died, and a number of people are unaccounted for following the blast.

And the Italian parliament has backed plans by the new Prime Minister Metteo Renzi for electoral reforms designed to ensure a more stable and long-lasting government. After securing a comfortable victory in the lower house of parliament, he twittered the message politics one, defeatism? Nill. As Alan Johnston reports from Rome. Mr. Renzi has also announced his economic plans.

He's ordered a tax cut for the poorest Italians. The tax burden will also be eased on businesses. They'll pay less for their electricity and huge debts owed to private companies by government agencies will be settled. So how will all these be funded? Well, Mr. Renzi insisted that much of it can be covered by spending cuts. There will also be a rise in capital gains tax.

BBC News.