Syrian government warplanes have bombed Kurdish-held areas of the northeastern city of Hasakah for the first time in the five-year-old civil war, according to fighters and a monitoring group.

The Kurdish People’s Protection Units (YPG), a key US ally in the fight against the Islamic State of Iraq and the Levant (ISIL) group, said on Thursday it would “not be silent” over what it called it an act of aggression.

There was no immediate comment from the Syrian government.

YPG spokesman Redur Xelil said the air strikes had hit Kurdish districts of Hasakah and positions held by a Kurdish security force known as the Asayish.

“There are martyrs and wounded,” he told the Reuters news agency.

Government forces were also bombarding Kurdish districts of Hasakah with artillery, and there were fierce clashes in the city, which is mostly controlled by Kurdish groups..

“Every hand spattered with the blood of our people will be held to account through all possible and available means,” the YPG said in a statement.

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The UK-based Syrian Observatory for Human Rights, which tracks the war using a network of activists, said warplanes had targeted Kurdish security forces’ positions in the northwest and northeast of Hasakah.

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It also said clashes were taking place in a number of places around the city.

The Syrian government, which routinely uses its air force against rebels fighting President Bashar al-Assad in western Syria, still has footholds in Hasakah and Qamishli, both in the Hasakah governorate.

The latest bout of fighting marks the most significant violence between the YPG and government forces since several days of fighting in Qamishli in April.

The YPG makes up a significant portion of the US-backed Syria Democratic Forces (SDF), a Kurdish and Arab alliance fighting ISIL, also known as ISIS, in Syria.

Last week the SDF, backed by air strikes from the US-led anti-ISIL coalition, said they had ousted ISIL fighters from the city of Manbij near the Turkish border after a two-month campaign.

Syria’s complex, multi-sided war has created a patchwork of areas across the country controlled by the government, rebels, Kurdish forces or ISIL.

Kurdish groups have exploited the collapse of state control to establish autonomy across much of the north.

Source: Reuters