A first Iranian flight has landed in the Yemeni capital, a day after officials from the Shia-controlled city signed an aviation agreement with Tehran.

The Mahan Air plane arrived in Sanaa on Sunday carrying a team from the Iranian Red Crescent and medical aid, an aviation official told AFP news agency.

Senior Iranian diplomats were on hand to welcome the flight - the first between the two countries in many years and comes weeks after Houthi Shia rebels took over the government in a coup.

Yemen's official Saba news agency, which is controlled by Houthis, said that under the deal Iran Mahan Air and Yemenia would operate 14 flights each a week.

Al Jazeera's Mohamed Vall, reporting from Aden, said not only have the Houthis opened this line but they have sent a delegation to Iran to discuss relations.

"The Houthis sent a high ranking delegation for the first time and they announced it. In the past they sent people to Iran but did not announce it, but now it is officially described as a government delegation.

"It is headed by the head of the political bureau in the Houthi movement and they are going to Iran to discuss bilateral economic relations," Vall added.

The flight underscores how the Shia rebels are strengthening their grip over state institutions and exercising sovereign power in Sanaa, even as the country's president, Abd-Rabbu Mansour Hadi, insists he is still in charge.

Blame game

Western-backed President Hadi, who fled last weekend an effective house arrest by the Houthis in Sanaa, slammed the agreement as "illegal," according to an aide.

"Those who signed it will be held accountable," Hadi said during a meeting with tribal chiefs in the southern city of Aden where he is now based.

Over the past days, Gulf countries have moved to support Hadi's claim of legitimacy, with Bahrain, Saudi Arabia, the United Arab Emirates and Kuwait moving their embassies to Aden.

Tehran has repeatedly been accused of backing the Houthis.

US Secretary of State John Kerry said on Tuesday that "critical" support of the fighters by Shia-dominated Iran "contributed" to the collapse of Yemen's government.

Iran rejected Kerry's "blame game," insisting that foreign intervention in Yemen would "further complicate the situation".

Source: Al Jazeera and agencies