President Xi Jinping and Premier Li Keqiang sent messages of condolence on Sunday to their respective Sri Lankan counterparts after the country was hit by multiple deadly bombings.

In his message to Sri Lankan President Maithripala Sirisena, Xi said he was shocked by the series of explosions in Sri Lanka, which caused large casualties, Xinhua News Agency reported.

"I, on behalf of the Chinese government and people, as well as myself, send my deep condolences to the victims, and my sincere sympathy to the injured and families of the victims," he added.

The Chinese government and people will firmly stand by the people of Sri Lanka and firmly support the Sri Lankan government's effort to maintain national security and stability, Xi said.

Premier Li sent condolences to Sri Lankan Prime Minister Ranil Wickremesinghe over the attacks.

Multiple explosions hit the South Asian country on Sunday, killing at least 290 people and injuring more than 500.

Sri Lankan Health Minister Rajitha Senaratne said at a news conference on Monday that a group called National Thowheed Jamaath - a militant Islamist group in Sri Lanka - was responsible for the bombings, while foreign links are also suspected.