A newborn baby was among at least 15 people killed in Myanmar military strikes at multiple locations over the weekend, including a maternity clinic and a school, an ethnic armed group, an aid worker and rights monitors said on Monday.

The bombings come as the military-backed government, attempting to rebuild diplomatic ties after years of isolation, escalates its campaign to retake territory lost to resistance groups that now control large areas of the country.

A spokesperson for the military-backed government did not immediately respond to requests for comment. It has previously said it is waging a legitimate campaign against "terrorists." On Sunday, airstrikes hit four townships in western Rakhine state, where fighting has been fierce in recent weeks as the Arakan Army, which controls most of the state, has neared the capital, Sittwe.

The strikes hit a bridge in Kyauktaw, locations in Kyaukpyu and Pauktaw, and a makeshift clinic and maternity ward in Arakan Army-held Mrauk-U, killing at least 12 people and wounding 32, an Arakan Army spokesperson and an aid worker said.

The week-old baby girl, who has a surviving twin, was due to return home the following day but was "crushed and killed when the building collapsed from the blast," said Mrauk-U-based aid worker Wai Hun Aung. Four other people, including healthcare workers, also died, he said.

A day earlier, an airstrike on Loikaw, in Kayah state near the Thai border, hit a school during classes, killing three students and wounding five, the Karenni Human Rights Group (KnHRG) said on Monday.

Thai fighter jets have been carrying out air patrols as the conflict has spilled over the border, damaging homes and injuring at least one person on the Thai side, Thailand's government said.

Thai Prime Minister Anutin Charnvirakul said his government has urged Myanmar to exercise caution to ensure the situation does not affect Thailand.

A Y-12 transport aircraft and a fighter jet dropped more than 20 bombs on the Loikaw school, according to KnHRG and Banyar Khun Aung, secretary of the Karenni Interim Executive Council, who said there were no military movements or clashes in the area.

"Targeting a school where young children are learning and repeatedly bombing is an inhumane act that amounts to a war crime," he said.

Myanmar has been in turmoil since the military ousted Aung San Suu Kyi's elected government in a 2021 coup, triggering a civil war that the United Nations estimates has killed 100,000 people and displaced more than 3.5 million.

Coup leader turned president Min Aung Hlaing's military has received support from China, India and Russia. His administration has gained increasing international recognition in recent months, including secret talks with US officials as the Trump administration reverses years of isolation.

But his forces are struggling to dislodge opposition groups and increasingly rely on airstrikes, powered by jet fuel obtained mostly from Iran in shipments disguised with sham paperwork, Reuters reported earlier this year.

United Nations investigators accused Myanmar's military in August of deliberate aerial attacks on civilian buildings including schools and hospitals.

Myanmar’s foreign ministry said in response to the UN allegations that the military “exercises maximum restraint to avoid civilian harm.”The weekend attacks follow a deadly wave of strikes a month earlier in Rakhine's Kyauktaw and Ponnagyun townships that killed at least 58 people at camps for internally displaced civilians, drawing fierce international condemnation.