A man is in custody after allegedly holding his pregnant girlfriend hostage in a seven-hour armed siege in Melbourne's west.

The 41-year-old man was allegedly armed with a hammer and a knife and holding his pregnant partner captive.

Senior Sergeant Nicole Warner, of Sunshine Police, said officers were called to a property in Thyra Street, Sunshine, around midnight, after the woman called triple-0 and it emerged the man was armed.

Police say the siege was sparked by a domestic dispute.

The stand-off lasted for seven hours before Special Operations Group officers were called in to forcibly remove the man from the house, police say.

He was taken to Sunshine Police Station, where he is assisting police with their enquiries.

"It was fairly tense in our attempts to resolve the issue," Snr Sgt Warner said. "Thankfully, it was resolved peacefully and without any major injury to anyone."

The woman was treated by paramedics at the scene.

"She's recovering and she's being examined by ambulance personnel," Snr Sgt Warner added. "She's been cleared to come back to the police station to make a full police statement in relation to the matter."