Navy intercepts asylum seeker boat

HMAS Broome intercepted the boat on Sunday evening about 11 nautical miles north of the Browse Island contiguous zone.

Home Affairs Minister Brendan O'Connor said initial indications suggested there were 18 passengers and four crew aboard the boat.

It is the 26th asylum seeker boat to be intercepted in Australian waters this year.

The group will be transferred to Christmas Island where they will undergo security, identity and health checks.

Their reasons for travel will also be established.

After the interception of a previous asylum seeker boat on Friday, the federal opposition claimed there were just 55 beds vacant at the Christmas Island facility.

"If we have another boat arrive in the next 24 hours, which is quite possible, then it's full," immigration spokesman Scott Morrison told AAP on Saturday.

"We'll very, very soon be at the stage where they'll be transferring people to the mainland ... in large numbers."

The government concedes asylum seekers could be housed in Darwin if the island's capacity is stretched.

"The government has been saying for some months the Darwin centre may be used as a contingency for irregular maritime arrivals but the decision has not been made," a Department of Immigration spokeswoman told AAP.

The government has conceded asylum seekers could be housed in a Darwin facility if the island's capacity is stretched.