At least 19 children were wounded when a primary school was hit by shelling in Myanmar's Rakhine state, a lawmaker and a military spokesman said on Thursday.

Clashes between government troops and ethnic insurgents have intensified in Rakhine, from where tens of thousands of people have been displaced since clashes began in December 2018, bringing new chaos to the region from which more than 730,000 Rohingya Muslims fled a military crackdown in 2017.

The Arakan Army, which recruits from the mostly Buddhist majority, has been fighting for greater autonomy for the western region from the central government.

Artillery fire hit the school in Khamwe Chaung village in Buthidaung township on Thursday morning, Tun Aung Thein, a local member of parliament, told Reuters by telephone. He said he did not know who was responsible.

"According to the health department, 19 students are injured and one is seriously injured," the lawmaker said.

A military spokesman put the number of wounded at 20, and blamed the insurgents for the attack.

"We medically treated the students at the nearby military post and sent five to the hospital," Brigadier-General Zaw Min Tun told Reuters by phone.

A spokesman for the Arakan Army, denied its fighters were responsible, saying they did not have such artillery, and blamed government troops.

The British embassy in Myanmar issued a statement urging an end to the violence, which follows the reinstatement last week of an internet shutdown in the region.

"The increased violence in Rakhine state over the past few days is causing misery for many of the people living there," said Dan Chugg, British ambassador to Myanmar.

"Today's reported shelling of a school on Myanmar's Children's Day, following recent deaths of women and children, highlights the impact this is having on innocent people."

The statement urged all sides to do their utmost to protect civilians and called on the government to lift the internet restrictions.

A months-long internet blackout in four Rakhine townships – including Buthidaung - and one in neighbouring Chin state had been lifted in September as peace talks sought to end clashes.

Officials cited "security requirements and public interest" for the reinstatement.