A clash between Nepal's government and its head of state over controversial citizenship legislation threw the nascent republic into turmoil on Wednesday, after President Bidhya Devi Bhandari refused to sign proposed amendments in the law.

The bill proposed, among other changes, to give citizenship certificates to children whose parents' whereabouts were not known. Under the amendments, children born to a Nepali mother but whose father is unknown could get citizenship documents after the mother makes a declaration.

The deadline for Bhandari, a ceremonial head of state under the 2015 constitution, to approve the amendment to the 16-year-old Nepal Citizenship Act, expired at midnight.

"Since the government and parliament did not address her concerns, the president has refused to approve the bill," Bhesh Raj Adhikari, an aide to Bhandari, told Reuters without giving details.

Legal experts said the president was required to approve the changes, passed twice by a majority of parliament.

Not doing so was a serious and grave violation of the constitution by a ceremonial head of state, said Balaram K.C., a retired judge of the Supreme Court.

“She should either resign as president or somebody should file a case against her in the Supreme Court,” he said.

Aides to Prime Minister Sher Bahadur Deuba said top leaders of the ruling alliance would meet on Wednesday to discuss the situation and political alliances for the upcoming national elections set for November 20.

Additonally, under the existing citizenship provisions, a foreign woman married to a Nepali men can get a citizenship certificate after she shows proof of her marriage and that she has initiated action to relinquish her foreign citizenship.

Surya Thapa, a senior leader of the main opposition Communist Unified Marxist Leninist (UML) party, said the amendment must include a provision requiring foreign women to wait for seven years before getting the Nepali citizenship.

(Reporting by Gopal Sharma. Editing by Gerry Doyle)