ALEPPO, Syria, Jan 7 - Fierce fighting resumed in Syria's northern city of Aleppo between government forces and Kurdish fighters for a second day on Wednesday, sending thousands of civilians fleeing and leaving at least four people dead.

The violence, and statements trading blame over who started it, signaled that a stalemate between Damascus and Kurdish authorities that have resisted integrating into the central government was deepening and growing deadlier.

Jan 6 (Reuters) - Fighting in the northern Syrian city of Aleppo on Tuesday left at least four people dead and several others wounded, state media said, with the government and the Kurdish-led Syrian Democratic Forces trading blame for the violence.

The clashes are the latest to break out in Aleppo as officials scramble to advance a deal to address Syria's deepest remaining fracture by merging the U.S.-backed SDF with the central government.

DUBAI, Jan 7 (Reuters) - Iran's top judge warned protesters on Wednesday there would be "no leniency for those who help the enemy against the Islamic Republic", while accusing Israel and the U.S. of pursuing hybrid methods to disrupt the country.

Tehran is under international pressure with U.S. President Donald Trump threatening to come to the aid of protesters if security forces fired on them, seven months after Israeli and U.S. forces bombed Iranian nuclear sites in a 12-day war.

Iranian Supreme Leader Ayatollah Ali Khamenei has vowed not to "yield to the enemy".

Syria's government on Wednesday demanded that Kurdish fighters leave the neighbourhoods they control in Aleppo following clashes between the two sides which saw thousands of civilians flee.

The Syrian government and Kurdish-led forces traded blame over who started the deadly clashes on Tuesday, which killed 16 civilians and one defence ministry member.

The violence comes as the two sides have so far failed to implement a March deal to merge the Kurds' semi-autonomous administration and military into Syria's new Islamist government.

Iran on Wednesday hanged a man convicted of spying for its arch enemy Israel, the judiciary said, the latest such execution on espionage charges in a trend that has troubled rights groups.

Ali Ardestani had been convicted of sharing information with Israel's spy agency Mossad and receiving money in the form of cryptocurrency in exchange, the judiciary's Mizan news agency said.

By Siyi Liu and Florence Tan

SINGAPORE, Jan 7 (Reuters) - Chinese independent refiners are expected to switch to heavy crude from sources including Iran in coming months to replace Venezuelan shipments halted since the U.S. removed the country's president, traders and analysts said.

Caracas and Washington agreed to export up to $2 billion worth of Venezuelan crude to the United States, President Donald Trump said on Tuesday, after U.S. forces captured Venezuelan President Nicolas Maduro over the weekend.

The United Nations on Wednesday said decades-long discrimination and segregation of Palestinians by Israel in the West Bank were intensifying, and called on the country to end its "apartheid system".

In a new report, slammed by Israel, the UN rights office said "systematic discrimination" against Palestinians across the occupied Palestinian territories had "drastically deteriorated" in recent years.

"There is a systematic asphyxiation of the rights of Palestinians in the West Bank," UN rights chief Volker Turk said in a statement.

NICOSIA, Jan 7 - Cyprus assumed the rotating presidency of the European Union on Wednesday, marking the start of its six-month term with a meeting in Nicosia attended by Ukrainian President Volodymyr Zelenskiy, European Commission President Ursula von der Leyen and European Council President Antonio Costa.

A Saudi-led coalition struck the home province of Yemen's UAE-backed separatist leader on Wednesday, after he failed to show up for talks in Riyadh and was kicked out of the country's presidential body.

The coalition said it had given Aidaros Alzubidi a 48-hour ultimatum to come to Riyadh for discussions, after his Southern Transitional Council (STC) grabbed swathes of territory last month.

But he failed to board the flight carrying his delegation, and the coalition struck his home province of al-Dhale after accusing him of mobilising "large forces" there.

Jan 7 (Reuters) - The leader of Yemen's Southern Transitional Council (STC), Aidarous al-Zubaidi, failed to board a plane set to take him to Riyadh, and fled instead to an unknown destination, the Saudi-backed coalition in the country said on Wednesday.

The remarks came amid efforts to end fighting that erupted last month between the STC, backed by the United Arab Emirates, and Yemen's Saudi-backed internationally recognised government, which has triggered a major feud between the Gulf allies.